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[I posted this to History, but it was suggested that History of Science and Mathematics would be a better choice. So I'm posting it here too.]

I’m working to build the Cavendish experiment of 1798 according to Cavendish’s own specifications. I have a question about building materials Cavendish may have used.

Cavendish put his pendulum inside a small building to protect it from wind and rain. The building has dimensions of approximately 3.5 meters. What kind of building materials Cavendish may have used in 1798?

You can see a scale model of the experiment. In the model they chose to make a brick building. Do you think this is what Cavendish used? Was cement in use then?

Cavendish calls this building a "room" and gives no other information about it:

...I resolved to place the apparatus in a room which should remain constantly shut...

Experiments to determine the Density of the Earth. By Henry Cavendish, Esq. F.R.S. and A.S., p.471

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Neither the original publication: Henry Cavendish, "XXI. Experiments to determine the density of the earth." Philosophical Transactions of the Royal Society of London, Vol. 88, 1798, pp. 469-526 (scan online), nor the annotated German translation: Henry Cavendish,"Versuche, um die Dichtigkeit der Erde zu bestimmen." Annalen der Physik, Volume 2, Part 1, 1799, pp. 1-62 (scan online) mention a separate building; they both just mention a room, presumably in an existing building.

As I was convinced of the necessity of guarding against this source of error, I resolved to place the apparatus in a room which should remain constantly shut, and to observe the motion of the arm from without, by means of a telescope;

From 1782 to 1810 Cavendish resided at a mansion: Cavendish House, Clapham Common, a picture of which is here. This was in the south of London, in the Borough of Lambeth. Best I can establish, this is where Cavendish conducted his experiments. For example, the Encyclopedia Britannica states:

Following his father’s death, Henry bought another house in town and also a house in Clapham Common, to the south of London. The London house contained the bulk of his library, while he kept most of his instruments at Clapham Common, where he carried out most of his experiments.

In this picture of the house shortly before, or during, its demolition it appears to have been constructed from brick masonry.

The book: Christa Jungnickel and Russell McCormmach, "Cavendish — The Experimental Life, 2nd ed.", Berlin: Max-Planck-Gesellschaft zur Förderung der Wissenschaften 2016 contains the following description:

Cavendish’s house has been called a mansion, but a better description of it from the time is “a tolerable good house, built with red brick.”

In comments OP raises the possibility of the experiment having been conducted in an outbuilding. The only specific reference to an outbuilding at Cavendish House that I could find in Jungnickel / McCormmach during a quick perusal is to a greenhouse mentioned in Cavendish's notes on experiments on air. Modern greenhouses consist largely of glass, which would rule them out as the location of the experiment, but methods of construction used for greenhouses may have been very different during Cavendish's time.

An 1877 map appears to show a group of three outbuildings at the far end of the Cavendish House property, but whether any of these existed in 1798 is impossible to know.

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  • $\begingroup$ On page 473, Cavendish writes: "The pieces of wood are fastened to the wall of the building..." royalsocietypublishing.org/doi/pdf/10.1098/rstl.1798.0022 And when I look at the cross section of this "building" it looks to me like a separate structure not a room in a house. (First image on this page cavendish-deneyi.com/parcalar.html) $\endgroup$
    – zeynel
    Apr 28, 2022 at 5:36
  • $\begingroup$ Also, according to Isobel Falconer, (who is an expert on Cavendish) he made the experiment in the garden of his house in Clapham, in a shed: p. 473 cavendish-deneyi.com/pdf/… $\endgroup$
    – zeynel
    Apr 28, 2022 at 5:39
  • $\begingroup$ Also on page 471 Cavendish writes: "Fig. 1. ... is a longitudinal vertical section through the instrument, and the building in which it is placed." So the balance was in a building of its own, not in a room in a house. $\endgroup$
    – zeynel
    Apr 28, 2022 at 8:23
  • $\begingroup$ Thanks for the Lambeth map. I wish we knew the scale. I would write my own answer but now I'm confused. I was sure that Cavendish did the experiment in his garden inside a building specifically built for this experiment. But not so sure anymore. See the map of an outbuilding in his garden and my comments there cavendish-deneyi.com/cavendish-outbuilding.html $\endgroup$
    – zeynel
    Apr 28, 2022 at 9:40
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    $\begingroup$ @zeynel That's an interesting find. I assume you did not know all these details prior to asking the question. Duplication of effort due to missing information in a question is one of my pet peeves. Note that the map you found is dated three decades after the experiment, and after Cavendish's death. There is no way of knowing whether that outbuilding was there in 1798. I read a remark in passing (can't find it now) that the next owners of Cavendish House made extensive alterations to the property. $\endgroup$
    – njuffa
    Apr 28, 2022 at 9:57

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