Pièce 62 - Letter from Richard Sheepshanks

4 pp.

RS gives various comments concerning faulty aspects of their respective barometers and the Cambridge telescope: 'I find I shall want a second quicksilver horizon on account of the telescope not being in the same vertical plane so that one cannot serve for the purpose I wish to try. I consulted [Edward] Troughton about the slits for the mural. He says he does not like to cut the building quite in two but he does not see any serious objection to doing so'. RS describes how he would pursue this plan (with a diagram). He has spoken to Troughton with regard to correcting for the expansion and contraction of the brass scale (on the barometer) when the temperatures at the upper and lower station are different. He gives the mathematical operation which makes this correction. Since writing the above he has seen Troughton who says he is 'against cutting the slits to the ground and would even prefer the raising the reflecting surface from the floor. This indeed might be easily done by having a little square pier thus [diagram] in front of the wall detached from it and covered by the floor. A stool which adjusted in altitude like a music stool might be placed upon it and thus take in all stars you wanted. Would not after all this be the cheapest and best way'.