The Induction of Klüver Visual Hallucinations

Abstract

Determining the triggers, neurological, sensory or physical, for Blake’s ‘visions’ cannot be done with complete accuracy. In Blake’s case the absence of a diary, journal or an extensive written correspondence distances him from being a subject completely capable of full historical retro-diagnosis. Nevertheless, this chapter will discuss visual hallucinatory types in conjunction with a consideration of their likely agencies of induction since some of them may have had a historical specificity unlikely to be paralleled today. It should be remembered throughout that ‘Hallucinations in psychologically normal individuals provide a valuable route to studying the neural mechanisms of visual awareness.’ The natural agency of ‘Scheerer’s phenomena’ has been discussed in Chap. 1 along with Munro Smith’s assigning of migraine aura to some of Blake’s images in 1909. Naturally occurring agencies may also include some triggers of migraine, such as photophobia, which appear to be reported by Blake’s contemporaries J.T. Smith and Allan Cunningham (both of whom, of course, would not have been able to access a vocabulary capable of arriving at a diagnosis of migraine). William may also have indulged in the popular contemporary electrical therapies known to have been used by Catherine Blake, c. 1800–1804. Finally, this chapter will discuss hallucinations caused by prolonged exposure to engraved lines on copper plates or the prints taken from them (‘Parallellinienfeld in einem Kupferstiche’), a method of induction used during the first scientifically recognized experiments recording visual hallucinations. Unsurprisingly, such methods of induction have long been superseded and forgotten much like the trade of copper-plate engraver that Blake followed.

Determining the triggers, neurological, sensory or physical, for Blake’s ‘visions’ cannot be done with complete accuracy. In Blake’s case the absence of a diary, journal or an extensive written correspondence distances him from being a subject completely capable of full historical retro-diagnosis. Nevertheless, this chapter will discuss visual hallucinatory types in conjunction with a consideration of their likely agencies of induction since some of them may have had a historical specificity unlikely to be paralleled today. It should be remembered throughout that ‘Hallucinations in psychologically normal individuals provide a valuable route to studying the neural mechanisms of visual awareness.’¹ The natural agency of ‘Scheerer’s phenomena’ has been discussed in Chap. 2 along with Munro Smith’s assigning of migraine aura to some of Blake’s images in 1909. Naturally occurring agencies may also include some triggers of migraine, such as photophobia, which appear to be reported by Blake’s contemporaries J.T. Smith and Allan Cunningham (both of whom, of course, would not have been able to access a vocabulary capable of arriving at a diagnosis of migraine). William may also have indulged in the popular contemporary electrical therapies known to have been used by Catherine Blake, c. 1800–1804. Finally, this chapter will discuss hallucinations caused by prolonged exposure to engraved lines on copper plates or the prints taken from them (‘Parallellinienfeld in einem Kupferstiche’), a method of induction used during the first scientifically recognized experiments recording visual hallucinations. Unsurprisingly, such methods of induction have long been superseded and forgotten much like the trade of copper-plate engraver that Blake followed.

Research papers on visual hallucinations commonly rehearse for readers the several modes of the inducement of the geometric type of visual hallucination.² Particularly good descriptions of neurally based hallucinatory triggers or inducing agents are given by Vincent A. Billock and Brian H. Tsou.³ These agents include (apart from migraine with aura), hypnagogic (falling into sleep) and hypnopompic (waking from sleep) states together with light deprivation and flickering light.

Some agents of induction look impossible or unlikely. To conduct his controlled experiments, from the 1920s onwards, Klüver mainly used mescaline as the inducing agent.⁴ It gave a predictable induction suitable for experimental settings using volunteer subjects. This substance would not have been available to Blake.⁵ There is some evidence tobacco usage can bring about Altered Consciousness States which may include the perception of Klüver-type patterns.⁶ Whether Blake smoked tobacco is not known but it is not necessary to suggest artificial agencies. Straightforward concentrated meditation can induce shimmering sparkles and bright rays of light and should not be ruled out, particularly if experienced in conjunction with transient hypnagogic or hypnopompic states.⁷ However, although this book has stressed migraine aura and Klüver-type percepts, the chapter will look more widely at a range of entoptic photons (basic units of light), including neurally generated phosphenes. Since light is a basic foundation for human consciousness, it not surprising a visual artist would want to examine and reflect upon such phenomena.

However, it is worth remembering that Blake insisted on the ubiquity of his ‘visionary’ faculty. He did not claim his capacities were unique, or even rare, but were generally distributed across the population. The far from credulous painter, John Linnell, an important patron from 1818 onwards and the person who commissioned the Illustrations of the Book of Job (1826), wrote that ‘Blake would occasionally explain unasked how he believed that both [John] Varley & I could see the same visions as he saw making it evident to me that Blake claimed the possession of some powers only in a degree that all men possessed and which they undervalued in themselves.’⁸ This sentiment was repeated by Crabb Robinson in 1852 (‘of this gift of Vision, he did not boast of it as peculiar to himself; All men might have it if they would’).⁹ And again by Blake’s first biographer, Alexander Gilchrist, in 1863: ‘As Blake truly maintained, the faculty for seeing such airy phantoms can be cultivated.’¹⁰

These comments suggest he thought of his ‘visions’ as naturally occurring phenomena, experiences not requiring artificial intervention. He probably called them ‘visions’ not only because he wanted to communicate using an older, more traditional, terminology which also included voice hearing but also because the visual types appeared on his retina, directly within his visual field through retino-cortical mapping. Of course, because V1 is a part of the cortex it is also a cognitive environment for images. With uncanny accuracy, Blake likened them to a ‘Vision … seen by the [Imaginative Eye] of Every one’ (E 555, italics and square brackets in E). That is, the faculty of ‘Vision’ is cognitive (because ‘Imaginative’), neurologically identical across the species and capable of being ‘seen by … Every one.’ At the very least, such sentiments about his understanding of the general distribution and prevalence of a ‘visionary’ faculty implies he considered it a condition rather than a disorder.

Migraine Aura

In the case of his earliest visual hallucinations, discussed in Chap. 2, the position is fairly simple. Blake dated, and even geographically located his first migraine aura-like episodes to Peckham Rye when he was ‘a child, of eight or ten,’ which would have been around 1766.¹¹ Klüver form-constants are a known co-modality of migraine aura and can be grouped within the geometric patterns structured from phosphenes formed by that disorder.¹² As one commentator puts it with respect to the Ermentrout and Cowan (1979) and Bressloff and Cowan, et al., (2001) models, ‘some of the patterns their network generates are strongly reminiscent of aura components.‘¹³ ‘Web shapes’ and ‘spiders webs’ motifs show up as eight examples defined and categorized in Podoll and Robinson’s Migraine Art, with their case history of sources identifying such percepts dating as far back as W.R. Gower’s paper on migraine of 1895.¹⁴ The specific agent of induction for Blake’s childhood experience of migraine, if Munro Smith’s identification is correct, was the transit of a migraine Cortical Spreading Depression (CSD) on his V1 and its retino-cortical mapping.

The term ‘depression’ refers to neural activation on V1 (which is why it is painful) caused by waves of polarized and depolarized neural activity travelling across this area of the cortex. A characteristic zigzag arc of phosphenes, forming fortification spectra, appears in the visual field, directly replicating the shape of the indentation. The first usage of the term ‘fortification’ to describe the spectra’s characteristic zigzag outline first occurred during Blake’s lifetime in a paper by the Quaker physician and naturalist, John Fothergill (1712–1780), entitled, ‘Remarks on That Complaint commonly known under the Name of Sick Head-Ach[sic].’ A ‘Sick Head-Ach’ was the contemporary pathological description for migraine. Read to the Select Society of Licentiates in 1778, Fothergill’s paper was printed posthumously in 1784. Fothergill provides a good phenomenological description: ‘the sick head-ach … begins with a singular glimmering in the sight; objects swiftly changing their position, surrounded with luminous angles, like those of a fortification.’¹⁵ His description of the spectra ends there abruptly. Likely causes of migraine were thought to include dietary, weather and vascular origins. Typically for the period, Fothergill thought his episodes were brought on by buttered toast.

Although Hubert Airy in 1870 knew of Fothergill’s paper, he refers to it only in passing.¹⁶ It seems unlikely Blake would have come across it although he may well have heard about Fothergill on account for his support for slavery abolitionist Granville Sharp (1735–1813) and prison reformer, John Howard (1726?–1790). Fothergill’s historical significance was to have described how these entoptic percepts, with geometric lines and shapes, angled at about 60° to each other, were characteristic of plan views of Renaissance and Post-Renaissance military fortifications. ‘Fortification spectra’ has become the standard terminology. It was not until the mid-twentieth century that two key papers correctly described migraine’s neurological basis. The first was Karl S. Lashley’s 1941 proposal that migraine propagates from V1.¹⁷ The second was the description of CSD in a 1944 paper by Aristides A.P. Leão.¹⁸ Significantly, this means that Blake would have had no concept of either migraine’s neurological origin or its pathological distinctiveness from other types of headache. Under such circumstances, Munro Smith’s BMJ communication of 1909, connecting migraine aura to Blake’s art, was an insight of considerable significance.

Phosphenes and Light Induction

Migraine aura is far from being the only agency of induction capable of triggering Blake’s ‘visions.’ Of potentially far-reaching importance are the findings of Anupama Nair and David Brang that, ‘after ∼5 min of visual deprivation, sounds can evoke synaesthesia-like percepts (vivid colors and Klüver form-constants) in ∼50% of non-synesthetes.’¹⁹ In candle-lit and oil lamp illuminated Georgian Britain, there would have been many daily incidences of light deprivation accompanied by the sonic intrusion of commonplace domestic and nieghbourhood sounds. Of course, such findings are consistent with Thomas Hobbes’ Leviathan (1651), that ‘a man shall in the dark, (though awake) have the Images of Lines, and Angles before his eyes.’²⁰ A degree of light deprivation may also be implicit in Blake’s several declarations (referred to above) about apparently hypnagogic and hypnopompic hallucinations.

However, the phenomenology of both migraine aura and Klüver form-constants are composed of a wide group of percepts known as phosphenes. These are the individual sparks of light and colour seen most readily through a vascular induction method when, for example, pressure from the fingers or hands is applied to the eyeballs. Assuming a neurobiological origin, it is likely that most of his visual ‘visions’ were comprised of phosphenes (from the Greek phos, light and phainain, to show), entoptic flashes of light propagated from V1. The neurophysiology of phosphenes is based on differences between inhibitor and activator neurons signalled from V1 and mapped onto the retina.²¹ They are the matrix of phenomena forming the basis of most of the visual hallucinations propagated from V1. Phosphenes occur naturally in migraine aura but are also capable of being triggered by vascular or electrical mechanisms (again, such as digital pressure on the eyeballs).²² Jearl Walker’s accessible introduction to their perceptual diversity (abridged here), gives some idea of their reported phenomenology: ‘shapes and colours that march and swirl across your darkened field of view … a bright center surrounded by a dark ring and a bright outer ring … a dark spot surrounded by a bright curved band … bright, colored and constantly changing … fine quadrangles in regular array, on which were either stars with eight rays, or dark or bright rhombs with vertical and horizontal diagonals … complex mazes … bright blue or red sparks … a dense network of bright lines on a dark ground … flickering … presumably because of the pulsation of blood.’²³

Phosphenes make up the very materials of migraine aura’s scintillating scotoma which, of course, is regularized into the patterns found in CSD. Billock and Tsou have discussed ‘the blurry distinction between phosphenes and Klüver forms.’ That is, phosphenes scaled up into clusters adopt the same symmetries as Klüver form-constants and migraine fortification spectra. As Billock and Tsou put it, ‘given the conceptual similarity of the Ermentrout-Cowan model to a reaction-diffusion system [Turing, 1952], a unified model that tackles the sequential development of phosphenes, fortifications, and Klüver geometries within a single migraine attack would be feasible … When phosphenes occur in large numbers (polyopia), they are often arranged in the same geometries as Klüver patterns.’²⁴ This reiterates the assumption made in Chap. 2 that, while migraine aura can be discriminated from Klüver form-constants, their common propagation from V1 makes them share not only a similar neurological configuration but, more crucially for a visual artist like Blake, a similar perceptual phenomenology.

Something that might have a bearing on Blake’s visual art is that there is some evidence migraine aura is perceived intensely coloured. One study reported that 22.22% of migraine with aura subjects saw ‘brighter colours’ during migraine attacks with one respondent adding, verbatim, ‘“colours get so bright that I feel they will attack me.”’²⁵ The possibility that Blake saw enhanced colours during migraine with aura or synaesthesia episodes may be suggested in his satirical poem ‘To Venetian Artists.’ In this he quips, ironically, ‘That God is Colouring Newton does shew’ (E 515). Superficially this is a comment on Blake’s well-known views about the unimaginative reception of the Opticks, but it may also be a straightforward endorsement that ‘That God is Colouring’ in the sense that colouring is enhanced by spiritual ‘Vision.’ In his annotations to Sir Joshua Reynolds’ Discourses on Art, Blake repeatedly repudiated Reynolds’ comments on Venetian art (‘The Venetian and Flemish schools … owe much of their fame to colouring,’ against which Blake scribbled, ‘because they could not Draw’). In its place, Blake claimed precedence for ‘Inspiration & Vision’ (E 646). It is possible, given the phenomenological characteristics of migraine with aura, that Blake saw more vivid colours during these episodes and increasingly came to associate them with God.²⁶

The stories of Blake’s ‘visions’ gathered by his contemporaries must be treated with a degree of caution but some of them seem to suggest a common trigger. The possible originating ‘vision’ behind Blake’s relief-etching, The Ancient of Days (1794), used as a frontispiece to his illuminated book, Europe a Prophecy (1794), was recorded by one of his earliest biographers. J.T. Smith, who knew Blake for about 40 years, but who did not write about him until 1828, commented that the image, ‘Represents “The Ancient of Days,” in an orb of light surrounded by dark clouds, as referred to in Proverbs viii.27, stooping down with an enormous pair of compasses to describe the destined orb of the world.’ In a footnote, Smith added a fascinating detail about its conception: ‘He was inspired with the splendid grandeur of this figure, by the vision which he declared hovered over his head at the top of his staircase.’²⁷

A muddled (although vividly written) parallel account by Allan Cunningham, dateable to 1830 but specifically relatable to a vision of Satan seems to record a similar—or even the same—moment of a ‘vision.’ Cunningham’s source may have come from personal or written contact with J.T. Smith (above) or with Blake’s widow, Catherine. Cunningham’s narrative adds several flourishes, not least by purporting to record Blake’s words, verbatim: ‘“At last I saw him. I was going up stairs in the dark, when suddenly a light came streaming amongst my feet, I turned round, there he [Satan] was looking fiercely at me through the iron grating of my staircase window. I called for my things—Katherine thought the fit of song was on me, and brought me pen and ink—I said, hush!—never mind—this will do—as he appeared so I drew him—there he is.” Upon this, Blake took out a piece of paper with a grated window sketched on it, while through the bars glared the most frightful phantom that ever man imagined.’ There is nothing extant which can be identified as this picture and The Ancient of Days is not usually thought of as a representation of Satan.²⁸ Interestingly, Cunningham began his narrative by commenting, ‘Visions, such as are said to arise in the sight of those who indulge in opium, were frequently present to Blake,’ a frustratingly oblique reference as to whether he did, or did not, use narcotics but also yet another corroboration of the circulation of the idea amongst his contemporaries that ‘Visions … were frequently present to Blake.’

Cunningham went on to describe how ‘Its eyes were large and like live coals—its teeth as long as those of a harrow, and the claws seemed such as might appear in the distempered dream of a clerk in the Herald’s office. “It is the gothic fiends of our legends, said Blake—the true devil—all else are apocryphal.”’²⁹ This apparently verbatim record of Blake testimony (‘“the gothic fiends of our legends”’) is noticeably acculturated, referencing the eighteenth-century gothic revival. Cunningham’s account suggests a point of origin for the light source which illuminates the darkness Blake was walking through (‘I was going up stairs in the dark’), a source powerful enough to bathe Blake in its light (‘“a light came streaming amongst my feet … through the iron grating of my staircase window”’). Indeed, Satan ‘glared,’ the being’s appearance distorted (‘Its eyes were large and like live coals—its teeth as long as … a harrow … claws … as might appear in [a] … distempered dream’). Both Smith and Cunningham agree that the vision was above Blake, ‘“I was going up stairs”’ (my italics). Cunningham also implies Satan was partially occluded because the manifestation appeared from behind ‘the iron grating of my staircase window … through the bars’ (my italics).

There is much which can be drawn out of these testimonies. Blake made his print of The Ancient of Days in 1794 but neither of the writers’ accounts dates earlier than 1828. Both writers concur that they are reporting a ‘vision,’ one which was implicitly without an external stimuli visible to others, including Catherine. Noticeably, in Cunningham’s account, ‘Katherine’ misunderstands her husband, thinking this is a ‘fit of song,’ suggesting not only similar events had happened before but that the onset of his visual hallucinations sometimes manifested at the onset of his lyrical writing. This might be consistent with types of grapheme-triggered synaesthesia resulting in Klüver-like form-constants reported by Nair and Brang, referred to above. That is, under certain conditions of light deprivation and ambient sonic intrusion, any amount of verbal discussion between William and Catherine about his being inspired to write might have been enough to trigger a cross-modal episode, something akin to synaesthesia, the subject of Chaps. 6, 7 and 8. In Nair and Brang’s experiment, which challenges the convention of any distinction between synaesthesia and other hallucinatory types, the inducing graphemes were the letters A-Z in Arial font which, under light deprivation conditions, triggered Klüver-like entoptic percepts. The trial respondents described these as ‘flashing lights,’ ‘a flash went off in my head,’ ‘a quick burst of light’ (the latter in a yellow ball). Nair and Brang argue that ‘(vivid colors and Klüver form-constants)’ occur ‘in ~50% of non-synesthetes’ after around five minutes of light deprivation. ‘These results challenge aspects of the cross-activation model and suggest that synesthesia exists as a latent feature in all individuals, manifesting when the balance of activity across the senses has been altered.’³⁰ Such spontaneous visual sensations would be consistent, not least, with the arguments presented in Chap. 7 about the Visionary Heads of c. 1819–1825, their night time induction and the convivial noise of Blake meeting his friends.

That Blake had to hand ‘a piece of paper with a grated window sketched on it,’ is also fascinating. This item could be a preparatory drawing, possibly one like his, Satan, Sin, and Death: Satan Comes to the Gate of Hell (1808) which shows the figure of Death standing in front of the massive horizontal and vertical iron bars of Hell’s gates visible through his transparent body.³¹ Alternatively, it might simply have been a gridded piece of paper Blake had lying around of the type he would have used in his commercial (or even his own) reproductive engraving profession for transferring images from drawings to copper plates via a technique known as ‘pouncing.’ Such a gridded paper exists associated with a drawing preparatory for a Jerusalem design.³² Klüver specifically names a ‘grating’ in his list of terms to describe the lattice form-constant.³³ In this case, the light from the window (referred to by Cunningham) may have been sufficient to trigger migraine, acting as a photophobic precipitant, one of the most common of the migraine triggers. Alternatively, with Cunningham’s description of an uncontrolled, partially occluded, ‘suddenly’ ‘streaming’ light, Blake’s vision may also have simply had ‘luminosity in the dark’ (because it was an entoptic image), a feature of migraine referred to as early as Hubert Airy’s essay.³⁴

While the evidence is far from conclusive, on the basis of Smith and Cunningham’s testimony about this staircase vision, the event (or events) they describe seem to be migraine aura episodes, the condition which seems to have resulted in the Peckham Rye ‘vision’ of c. 1766. The ‘grating’ is particularly significant because stripes and chequerboard patterns are known to induce migraine.³⁵ Again, in assessing this as credible evidence, either way one must also discount for the misreporting of phenomena not fully incorporated into the medical vocabularies of 1828 or 1830. An interesting confounding of descriptive terms might have arisen with Cunningham’s account of Blake’s hallucination of Satan having eyes ‘like live coals—its teeth as long as those of a harrow, and … claws.’ Nearly 30 years later, Airy’s paper cited testimony about (what is now known as) fortification spectra with its scintillating scotoma, which he described as having a ‘serrated outline, with smaller teeth at one end than at the other, its tremor, greater where the teeth are greater … its tinge of scarlet.’ ‘Teeth’ are used several times in the paper to describe the phenomenon of fortification spectra as Airy’s contemporaries struggled to collate and identify what was obviously a widespread but poorly understood condition.³⁶ The ‘teeth’ and ‘claws’ of Blake’s untraced Satan may reflect this aspect of the aura, implying imagery consistent with the migraine aura study whose participant reported not a Satanic entity but, ‘“colours … so bright … I feel they will attack me.”’³⁷

Blake may have recognized some of migraine’s triggers without, of course, understanding what they were. The Ancient of Days picture of Urizen in the sun suggests one of the frequently occurring triggers of migraine: photophobia, discomfort caused by glaring light.³⁸ Some 30%-60% of migraine episodes are triggered by glare.³⁹ Of course, spiritual light understood as a metaphor for religious revelation has a long history in Christian poetics. Consistent with a visual hallucination including (what may have been) pain and a potential source of glare is Crabb Robinson’s 1852 testimony of a meeting face-to-face with Catherine and William when they were ‘speaking of his Visions she said—“You know, dear, the first time you saw God was when You were four years old And he put his head to the window and set you ascreaming[”].’⁴⁰

The accounts of Cunningham, Smith and Crabb Robinson, like so much else to do with reports of Blake’s ‘visions,’ may only signify that he was occasionally subject to migraine attacks. However, whatever their origin, he or Catherine thought them sufficiently significant to pass on their occurrence as testimony to others who were interested in his ‘visions.’

Electrotherapy

In a fascinating but overlooked paper, the neuroscientist G.D. Schott in the leading British medical journal, The Lancet, has specifically linked Blake’s ‘falling star’ of Milton a Poem in 2 Books (1804–1811) to the contemporary physician John Birch’s electric healing therapies whose regimens were known to both Blake and his wife, Catherine (E 110). John Birch (1745–1815) had written of ‘electrical fluid’ being directed from an electrical machine ‘in the form of a star’ and which Schott links to two images in the illuminated book, Milton a Poem, a work Blake had begun, c. 1804. Birch was a socially significant therapist, styling himself ‘Surgeon Extraordinary to His Royal Highness the Prince of Wales, and one of the Surgeons to St Thomas’s Hospital.’ As Schott notes, the publication of Birch’s book, An Essay on the Medical Application of Electricity (1804), coincides with the time Catherine Blake was trying Birch’s cure.⁴¹

Blake wrote to William Hayley in December 1804 telling him, ‘My wife continues well, thanks to Mr Birch’s Electrical Magic,’ and claimed that ‘Electricity is the wonderful cause’ of reduced swelling in her legs (23 October 1804; 18 December 1804, E 756, 759). Blake’s patron, Thomas Butts, also seems have known Birch because his son, Thomas, Jr., wrote in his diary for 10 September 1800, ‘Mr. and Mrs. Blake, his brother [James, 1753–1827], and Mr. Birch came to tea.’⁴² This tea-party was six days before William and Catherine left London for Felpham but it is possible the Blakes had known Birch as early as the mid-1780s. At that time the entymologist Henry Smeathman, living in Paris had written to William’s long-time friend and patron, George Cumberland, in 1784 recommending he contact the ‘very ingenious Philosopher,’ ‘Mr Birch Surgeon in the Strand.’⁴³ Thanks to Angus Whitehead, our knowledge of Cumberland’s role as an intermediary between Blake and London’s more orthodox medical world has recently been expanded.⁴⁴ It is also useful to read Schott’s essay in conjunction with information about other practitioners and electrical machine makers active in London around that time.⁴⁵ There is good evidence of a number of networks of electro-mystical-therapeutic sociabilities surrounding the Blakes and their London-based circle of skilled artisanal craftsmen.⁴⁶ Amongst others, the Blakes may already have come across similar electrical therapies described by Richard Lovett and the Methodist evangelist, John Wesley. ⁴⁷

That the Blakes owned, or had access to, an electrical generation apparatus is evident since they needed one to produce the therapies Birch claimed as efficacious and which Catherine Blake clearly thought she benefitted from. Gilchrist records about Catherine that ‘she, too, learned to have visions; to see processions of figures wending along the river, in broad daylight.’⁴⁸ The notion that she ‘learned to have visions’ may indicate the possibility of such an electro-medical interventions just as their movement and evident luminous nature (‘figures … in broad daylight’) may suggest phosphenes (my italics). Electrical knowledge and religious mysticism as a species of showmanship have long been known to be interrelated but the Blakes’ use of an electrical machine at home provides a domestic context for such practices.⁴⁹

Blake’s arrival in coastal Sussex, by default, meant that he needed to write letters and his surviving correspondence for the years 1800–1803 has left a much better picture of his activities than is available for the 1780s and 1790s. When they arrived, Blake wrote to John Flaxman in a heightened state of sensitivity, ‘Felpham is a sweet place for Study, because it is more Spiritual than London[.] Heaven opens here on all sides her Golden Gates’ (E 710). On account of their journey being delayed by a few days, Blake had written to his patron there, William Hayley, to reassure him of his imminent arrival, stating, ‘My fingers Emit sparks of fire with Expectation of my future labours’ (E 709). Passing sparks across limbs of the body, even across people, as part of a showman’s act was well known in the eighteenth century. At the very least, Blake would probably have been aware of static electricity as the sources of such phenomena.⁵⁰

As part of this general upsurge in the popularization of electricity, Birch had already published A Letter to Mr. George Adams, on the Subject of Medical Electricity (1791).⁵¹ Included in it was a letter on ‘Medical Electricity’ providing a series of case histories of his treatments, including an alleged resuscitation after a suicide in May 1789. A man had hanged himself (with a silk handkerchief), was rescued and hurried to St. Thomas’ Hospital (where Birch worked), a Mr. Johnson, Jun. bled him and applied electrical treatment. The man was ‘re-animated instantaneously by the shock,’ his only memory of the hanging being ‘a pleasing sensation of green fields (colours) before his eyes.’ However, by far the most significant aspect of this particular case is that the man ‘recollected nothing till the electric shock, which he described as balls of fire darting through his eyes.’⁵² These ‘balls of fire darting through his eyes’ are good candidates for being amongst the first recorded electrically triggered phosphenes.⁵³

While only Catherine Blake’s ailments and electrical therapies are recorded (William reported her ‘stiff-knee’d but well in other respects’ in May 1804), she was reported by her husband as, ‘surprisingly recovered. Electricity is the wonderful cause’ on 23 October 1804 (E 749, 756). It is perfectly feasible William tried the therapies himself. The Blakes’ three-year sojourn at Felpham, ostensibly under Hayley’s patronage, was a difficult time. Not only was William’s relationship with him awkward, in 1803 he had been put on trial (and acquitted) at the local assizes on a charge of sedition following a fracas with one of the many dragoons stationed in the area readying for a French invasion. In the October 1804 letter, written to Hayley after their permanent return to London, he evidences some degree of past psychological distress, claiming to ‘have entirely reduced that spectrous Fiend to his station, whose annoyance has been the ruin of my labours for the last passed twenty years of my life’ (E 756). The notion of a ‘Spectre’ (as in ‘spectrous Fiend’) has a number of special meanings in Blake but, in this example, he is clearly referring to some kind of recurrent mental health disability damaging his creative life.⁵⁴ What Blake is announcing, of course, is a period of recovery from low spirits. In a letter of July 1800, he had referred to his ‘stupid Melancholy’ (E 706–7).

It is possible Birch’s electrical therapies were not solely applied to Catherine’s knees. Birch had used transcranial electrical shocks to treat ‘melancholy’ and, on the basis of his knowledge of Birch’s experiments, it is not impossible Blake tried a crude form of Electroconvulsive Therapy (ECT). Birch had, apparently successfully, used ECT in 1787 on an East India Company porter who had been referred to him for assistance because of being in ‘a state of melancholy’ (‘he sighed frequently … was inattentive to every thing … his pulse weak and low’). Birch ‘passed six small shocks through the brain in different directions.’ He had also tried, again with apparent success, ‘passing shocks through the head’ of an (unnamed) professional theatre singer as well as treating a 26-year-old man who had ‘a moping melancholy.’⁵⁵ While there is no direct evidence suggesting Blake self-administered ECT to overcome his ‘melancholy’ (the contemporary catch-all term for temporary depressive mental ill-health), the couple already possessed, or had access to, an electric generation machine for Catherine’s therapy and they had both met Birch, a person pioneering ECT and whose medical regimens they apparently both trusted and followed.

Flicker-Light-Induced Hallucinations

However, if the likelihood of Blake experiencing phosphenes during electro-therapy is slender, and the evidence—such as it is—is in any case restricted to a date range of 1800–1804, the possibility that he experienced visual hallucinations as a direct by-product of his work and training as an engraver, is a possibility of much greater magnitude. The evidence supporting this supposition comes in the early work of the Bohemian (present day Czech Republic), anatomist and physiologist, Jan Evangelista Purkinje (Purkinĕ) (1787–1869).⁵⁶ In his doctoral dissertation at the University of Prague in 1819, published in the German language in Prague in 1823, Purkinje produced the first scientific report on flicker-light-induced phosphene pattern hallucination.⁵⁷ Crucially, some of the experiments Purkinje conducted, with himself as the subject of the experiment, used the engraved lines of copper-plate prints to induce visual hallucinations. Since the results of Purkinje’s experiments arose from looking at either copper-plate prints or copper plates themselves, he would have exposed himself to the same sets of conditions Blake encountered every day of his working life as a printmaker.

The flicker-light-induced hallucinations Purkinje reported are related to migraine aura and Klüver form-constant hallucinations as well as to visual auras now associated with epilepsy and Ganzfeld-induced hallucinations (percepts triggered by experiencing a completely homogenous visual field—imagine the inside of a ping-pong ball).⁵⁸ The phenomenon of flickering, of course, is the characteristic signature known as ‘scintillating’ in migraine aura. Recent military aerospace research has also become interested in flicker-induced hallucination types, as reflected in the work of Billock and Tsou, apparently aimed at understanding fast, high altitude, military aviation.⁵⁹ To be precise, the sets of experiments Purkinje conducted, and which are assigned here as relevant to Blake, are not strictly flickering-light-induced hallucinations (which seem to need a flicker rate above 3hz—fast enough to be slightly uncomfortable to most people) but, rather, afterimage visual effects. However, afterimages (which can have a positive or a negative luminescence, sequentially) are probably retinal in origin but processed in the cortex.⁶⁰ Afterimages can also be produced by digital pressure on the eyeballs.

Interestingly, Purkinje’s initial method for inducing the first recorded flicker hallucinations was no more complicated than simply looking at the sun between his own, moving, spread out, fingers.⁶¹ Like the ‘light … streaming … through the iron grating’ of Blake’s staircase window in Cunningham’s report, the flickering effect of obstructions in front of light sources may be enough to cause photophobic hallucinations. However, some of Purkinje’s experiments were based on staring at printed engravings, both stationary and moving.

Appended to Purkinje’s Beobachtungen und Versuche zur Physiologie der Sinne (Prague, 1823) is an (unfortunately, rather small), single etching giving several examples of his entoptic percepts. This plate remains a frequently cited, ground-breaking, representation of the phenomena, the first recorded set of illustrations of visual hallucinations empirically derived. Purkinje’s experiments, for the first time, defined the complexities of the boundaries between objects and visual perception. Purkinje noticed that while the spatial properties of objects observed do not change (although they may be subjected to motion), the subjective percepts they provoke alter. Or, as Blake put it in a posthumously recorded poem, ‘the Eye altering alters all’ (E 485). Although the phenomena Purkinje observed, discussed below, were not entirely based on flickering light experiments (although he clearly sometimes imposed motion against bright backgrounds on the some of the objects he used), the 3+hz flicker rate which induces flicker hallucinations is the same as the flicker rate of migraine aura scintillating scotoma.⁶² An experiment where he used his fingers to interrupt sunlight (and create a flicker effect) was followed by one where he used a flickering candle flame to induce some of the patterns he reports, including the hexagons and zigzag percepts shown in his single etching.⁶³ It is likely zigzag percepts arise from the same neural signals on V1 as those experienced in migraine aura.

In Blake’s remarkable formulation of the spiritual powers of etching, it is the acids of the etching process which reveal ‘the infinite which was hid.’ Of course, etching is the basic process described in the illuminated book The Marriage of Heaven and Hell (1789–90): ‘But first the notion that man has a body distinct from his soul, is to be expunged; this I shall do, by printing in the infernal method, by corrosives, which in Hell are salutary and medicinal, melting apparent surfaces away, and displaying the infinite which was hid’ (E 39). This description is foundational to understanding the primacy of his imagery drawn from the techniques of printmaking in the illuminated books, all of which used etching processes.

Blake’s physical exposure to etching and engraving processes are dateable no later than 1772, the year he entered his apprenticeship. Unlike today’s artist printmakers, he learned his etching and engravings skills on an entirely commercial basis during his apprenticeship in the busy workshop of James Basire (1730–1802), master engraver, an indenture which began on the 4 August 1772 and lasted until 1779.⁶⁴ The paradigm of the artist printmaker, and its lack of current purchase on commercial image reproduction, has been noted by Morris Eaves: ‘Today it is difficult to explain the cultural role of a Basire or a Woollett because methods of reproduction more efficiently coordinated with the printer’s press and painter’s palette replaced engraving as Blake knew it. The craft now survives largely, if marginally, as a minor vehicle for “original” work in the “graphic arts” tier of the “fine arts” departments of art schools and universities.’⁶⁵ In the years after his apprenticeship he completed 19 book illustration commissions before the end of 1789, the cut-off date by which it is known he had acquired sufficiently accomplished mirror-writing skills in relief-etching to produce All Religions are One (c. 1788), There is No Natural Religion (c. 1788), Songs of Innocence (1789) and The Book of Thel (1789). Some of these commissions meant he was working at a fairly rapid pace since they called for the production of multiple plates. The one for Joseph Ritson’s three volume, Select Collection of English Songs (1783), required nine plates, for example.⁶⁶

Just taking the period 1788 to 1794 on its own, Blake produced a large number of mixed method intaglio engraved and etched commercial prints. These comprised 11 separate commissions, some of them requiring multiple plates. For example, 45 copper plates were required for Christian Gotthilf Salzmann’s three volume, Elements of Morality (1791), but all of them were returned to him again for re-working for the 1792 and 1793 editions when he added new lines of detail or emphasis as well as, not least, probably re-cutting worn grooves.⁶⁷

His life-long career as book illustrator necessitated working on copper plates using this so-called mixed method of etching and engraving. Copper-plate prints of the type he worked on commercially were made up of a series of fine almost parallel lines whose varying distances created the illusion of depth. Engravers worked in extremely close proximity to their copper plates. Blake’s paradigms of engraving were the commercial practices he learned both as an apprentice at Basire’s and, subsequently, as a self-employed engraver of commissioned book illustrations. One of the last remaining professional intaglio and stipple copper engravers, working into the twenty-first century, was Paul Holdway, one of a small team of engravers employed by the Spode Factory, Stoke-on-Trent, in the production of transfer printed ceramics, using techniques basically unchanged since Blake’s day. I was privileged to meet Paul and his colleagues on a visit to the Engraver’s Workshop at the Spode Factory in 2006 before it closed (very probably the last surviving example in the world). Photographs of the Engraving Team at work show very clearly the working conditions which cannot have changed much since the eighteenth century. Holdway has written that, ‘all engravers’ work is so detailed that it is usually undertaken with the aid of a magnifying glass.’⁶⁸ A photograph of a Spode apprentice at work shows not only the close proximity to the copper plate required but also the engraver’s compasses lying to hand, the signature motif of The Ancient of Days print.⁶⁹

Spode Engravers’ Workshop practices, even in the twenty-first century, were demanding. For stipple engraving, which Spode particularly favoured, they used a hand-held punch in conjunction with a hammer for the matrices of indentations required on the copper plate. Of this, Holdway writes, ‘Punching is very close work and could only be undertaken in good daylight.’⁷⁰ To these stresses made upon sight, one must also add duration. ‘A copper for a blue printed dinner plate with an all-over design … is about two months’ work for an engraver. That for the largest dish would take perhaps six months.’⁷¹ He is, of course, referring to normal office hours, an eight-hour day worked five or six days a week.

There is even a possibility, as argued by Lane Robson and Joseph Viscomi, that his late life was considerably discomforted, and his death possibly hastened, by cumulative poisoning by copper fumes from etching acid inhaled over many years.⁷² A 2005 study of migraine-affected artists reported that studio-associated odours could be a trigger (26%) for migraine attacks. Materials cited by respondents included turpentine, mineral spirits, oil paints and moist watercolours, albeit mainly odours connected with modern solvents. Their study is particularly interesting because it demonstrates that through various techniques of avoidance, deferral and intervention, migraine-prone artists are still able to continue with their art (although the study was not able to investigate the personal meanings of their art).⁷³ However, it is Jan Purkinje’s use of engravings or etchings as inducing agents for his experiments which is particularly striking.

Engraving and Hallucinations

The importance of Purkinje’s findings for the purpose of this study is that, among other types of induction, some of his reports involved him looking closely and fixedly at the near-parallel lines of prints produced by impressions on paper taken from copper etchings and engravings (‘Parallellinienfeld in einem Kupferstiche’). Purkinje’s use of etchings or engravings to provoke hallucinations, contemporaneous with Blake, makes Purkinje a particularly interesting analogue.

This is how Purkinje describes his basic type of experiment: ‘XV. For some time I have noted an unclear glimmering when I looked steadily at a field of parallel lines precisely engraved on a copper plate [print]. When I move the page forward or backward or around a central point, the vision reveals blurry streaks and the individual lines become undistinguishable. When the lines are horizontal, the streaks are also horizontal but somewhat irregular. The vertical lines remain vertical, whereas in a field of concentric lines the shadowy segments move in a circle. For a long time I was unable to interpret the phenomenon.’⁷⁴ Purkinje’s report of ‘unclear glimmering,’ ‘blurry streaks,’ and ‘shadowy segments mov[ing] in a circle,’ appear to be flicker-light-induced phosphene afterimages caused by ‘mov[ing] the page forward or backward around a central point.’

To get some idea of what Blake might have seen as entoptic images when he looked at engravings, one can turn to another of Purkinje’s experiments: ‘If I fixate on the parallel lines of a sharply drawn engraving for 15 to 20 seconds and then close the eye, there appears in the same place a scintillation of undefined light and dark zigzag lines, which run like waves through one another and perpendicular to the previous fixated lines. This scintillation lasts for a slightly shorter time than the initial viewing … The principal requirement is that the lines must be very close to each other.’⁷⁵ Purkinje’s experiment of seeing areas of scintillating light and ‘zigzag’ lines after looking at a ‘sharply drawn engraving’ (noticeably not one given motion) suggests some intriguing possibilities. Assuming, as has been argued here, Blake probably had early life onset of migraine with aura, c. 1766, then his daily work as an engraver, beginning with his apprenticeship in 1772, forced him to repeatedly experience the characteristic zigzag percepts he also experienced in migraine. Indeed, Purkinje’s experiments establish that Blake’s career spent etching and engraving is a sufficient cause of these percepts. To these experiences can be added the perceptual burden, particularly in engraving but also true of relief-etching, of estimating depth and orientation as he worked around a copper plate, incising engraved lines or estimating depth for the etching needle. These factors can be quantified and are known to progress as straightforward linear increases depending on the percentage of their variation from the picture-plane. Incisions oriented nearest to 90 degrees away from the picture plane are perceived slowest, the fastest are those in line with the picture plane.⁷⁶

Of course, he might have practised avoidance techniques in the workplace but the effects would have had an impact because Blake engaged with these processes all of his working life. While one must allow a marginal effect for their different physiologies, unless Blake was neurologically different from Purkinje, given the same conditions they would have experienced similar entoptic percepts. The same visual events Purkinje experienced would also have occurred to Blake, not just when viewing prints closely (as he must have needed to do professionally), but also while etching or engraving lines on copper plates, with or without flickering candlelight. Gazing intensely at near-parallel engraved lines, either printed or on the plates, would have been part of Blake’s daily life as both artistic printmaker and commercial engraver. In follow-up experiments in the 1950s, perceptions of moving images (including rotating ‘chrysanthemum’ shapes) were created by viewing radiating, parallel concentric and linear sets of lines, confirming Purkinje’s findings.⁷⁷ Further experiments in the 1990s, accompanied by a literature review of the evidence, concluded that these percepts were not likely to be caused by disrupted optical accommodation of the patterns but were more likely to have been triggered by some imprecise area of the cortex, possibly involving V5.⁷⁸

Producing ‘a field of parallel lines precisely engraved’ was Blake’s professional occupation. He was apprenticed to it from his early teens. Images made by engraving or intaglio etching were built up by creating differing distances and angles between matrices of parallel lines. The basic technique was hatching and cross-hatching, the cutting of near-parallel lines which intersected and crossed over other sets of near-parallel lines at an acute angle. This formed a distinctive lozenge shape. The nearer together the lines were cut, making the resulting lozenge shape smaller, the darker the visual effect. Widening the gap between the lines and, consequently, making the lozenges bigger, the lighter the effect. To add tone, one could also put a dot (a flick of the engraving tool) in the middle of the lozenge. Again, the nearer the dots to each other in their lozenges, the darker the effect, the further apart, the lighter. It was through this means that engravers slowly, and laboriously, built up complex images of faces and hands and, indeed, all the visual elements of the prints. That Blake learned these techniques and employed its terminology, is shown in a remark he made disparaging Thomas Stothard, a successful painter and engraver (who Blake felt had plagiarized his Chaucers Canterbury Pilgrims fresco): ‘… his blundering blurs can be made out & delineated by any Engraver who knows how to cut dots & lozenges’ (E 572). As will probably be clear by now, these ‘lozenges’ are simply another acculturated description of the lattice form-constants of visual hallucination defined by Klüver.⁷⁹ Whether in his visual hallucinations or in his day-to-day workshop practice, Blake was never far away Klüver patterns.

There is a further complication to understanding the perceptual neurophysiology of cross-hatched lozenge engraving and etchings techniques, and how engravers built up their images. It has only been comparatively recently understood that matrices of grid-like shapes, when made into visual art, are perceived and re-ordered by the brain into illusions of shape (of a face, a hand etc.) according to their individual size and not by their individual shape. Although the cross-hatched lozenge is the standard unitized technique for eighteenth-century printmakers practising line engraving, it is the size—and not the shape—of each lozenge or cross-hatched element which is crucial for perceptual re-assembly of each element into a picture. These effects are known to be neural and not optical.⁸⁰ Blake would have dealt with the challenges posed by this in a pragmatic way, something which clearly benefitted from the skills he learned and developed over a lifetime. While such perceptual challenges are not pathologically disruptive, line engraving clearly placed on its practitioners’ extra burdens on visual acuity, manual dexterity and motor co-ordination.

It is not proposed that Blake’s planographic-prints-induced visual distortion or hallucination (although the prints themselves may contain evidence of his cognitive responses to visual hallucination). For example, The Song of Los (1795) plates 1, 2, 5 and 8 are printed by a planographic method and The Book of Los (1795) plates 1–3 and 5 were printed from their surfaces with only light etching for the outlines. Of course, all of these works fall into the category of Blake’s mid-1790s prophetic mode, with The Book of Los having for its frontispiece (plate 1) a depiction of, Eno, a female prophetic character uttering her prophecy. There are acknowledged difficulties of measuring neural responses to tonal qualities in paintings.⁸¹ Noticeably, although Purkinje would no doubt have had access to mezzotint engravings or other tonal types, he did not use them for his experiments. No adequate methodology seems to exist, to date, which might be employed for this type of analysis of the tonal properties of prints. Current inquiries into painting and visual perception treat edges and contours (usually discriminated into ‘soft’ or ‘hard’) as factors mobilizing degrees of learned aesthetic response but the engraved or etched lines of prints do not yet seem to have been considered.⁸²

The ‘dots & lozenges’ techniques of eighteenth-century printmakers produced thousands and thousands of edges (eight per lozenge, comprised of the inside and outside of each line), each of which the eye perceives, compares to a ground and compiles into an image. The matrices of parallel lines also offer quantifiable sets of thickness and frequency. Hatching and cross-hatching have been proposed as possible determinants for methods of face recognition in transposing freehand sketches into legible systems but, so far, without examining qualities such as line frequency.⁸³ The extraction and analysis of lines and angles in images (principally digitized) has also been proposed as projecting defined correlates with human emotions but, again, without any consideration of the medium or support (e.g. paper, canvas, etc.) in the case of non-digital imagery.⁸⁴ This is odd because the neural fundamentals of object recognition are understood and can be calibrated.⁸⁵ Potentially, the lines and edges of prints produced by conventional etching and engraving afford excellent opportunities for understanding the neural role of edges and contours in visual perception.

Finally, it may be asked whether any other contemporary commercial engravers or printmakers experienced hallucinations?

The answer is that at least one of them did. This was the London copper-plate printer, William Bryan, the friend of the poet—and eventual Poet Laureate—Robert Southey.⁸⁶ Bryan has been referred to in the Introduction and Chap. 3 on account of his proximity to Blake as another person working in London’s printmaking trade, c. 1790, who shared an affinity with the religious doctrines of Emanuel Swedenborg, someone whose visual and auditory hallucinations are well recorded. Although Bryan seems not to have produced or issued prints in his own name, as a commercial copper-plate printer he would have had some engraving skills, certainly sufficient to effect small repairs or to level distorted plates he was printing from (a typical use for Blake’s trope of ‘the Hammer of Los’). From premises in Dorset Street, Marylebone, in the mid-1790s he was a testifying follower of the prophet, Richard Brothers (self-styled ‘Prince of the Hebrews’). He also seems to have had earlier links to a Swedenborgian society in Avignon, France (although he later wrote a manuscript disavowing Swedenborg). Emanuel Swedenborg, of course, was a significant figure for Blake, mentioned several times in The Marriage of Heaven and Hell (1789–90) and referenced as a ‘visionary’ in A Descriptive Catalogue (1809) as the inspiration for his (untraced) Spiritual Preceptor painting in the accompanying exhibition (E 546).

Bryan’s accounts mainly evidence mixed modality visual and verbal auditory hallucination. For example, he had one of these hallucinations while walking on the road between Marlborough and Devizes in 1794: ‘the night was dark, there being no moon, and overcast so that no stars could be seen, an astonishing light surrounded me, so that I could see in a circle of about an acre all things round me, as if in the day time, I heard a voice pronounce, in a very awful tone, the following words: “Woe to the city of Bristol! the cry of innocent blood is against it: it shall be shaken, and fall.”’ Bryan’s vision, in keeping with contemporary abolitionist sentiment, was politically inflected in being a declaration against what he knew to be Bristol’s ‘traffic in slaves.’⁸⁷

However, an earlier hallucination of a less clear type occurred when Bryan was printing at his press: ‘The 23d of the month called January, 1789, in the morning, having made all things ready for my work, which was then copper-plate printing, I found a stop in my mind to go on with it. Waiting a little, I took some paper to wet for another plate, but found the same stop: then I perceived that it was of the Lord.’⁸⁸ Whatever the sensation of the presence (‘a stop’) Bryan experienced, dampening the paper to prevent it tearing was a crucial stage in the printing process. That he seems to have been about ‘to wet’ the paper ‘for another plate,’ implies he would have recently given the new plate a final inspection. It was evidently at this point of close contact Bryan had his vision. There were many potential inducers for the visual hallucinations Blake experienced. On balance, it seems likely that he would have experienced most of them at one time or another.