A Letter from James Ferguson

Buried in Haverford College’s Quaker and Special Collections is a substantial collection of autographed letters and other miscellany. Many letters were written by astronomers, mathematicians, naturalists, and others we might call (problematically or not) scientists.[1] Leafing through the collection recently, I came across this letter from James Ferguson on behalf of Lord Charles Cavendish. Writing on 5 July 1765, Ferguson seemed to be trying to get some equipment to carry out experiments on the compressibility of water and other liquids (if the note at the bottom of the letter is accurate).

In the previous few years John Canton had published in the Philosophical Transactions his results on the compressibility of water and other fluids, his “Experiments to Prove That Water is Not Incompressible” 52 (1761–62): 640–643 and his “Experiments and Observations on the Compressibility of Water and Some Other Fluids” 54 (1764): 261–262. The first paper described a his experimental apparatus and reported his findings, that water was compressible. His results disproved commonly held beliefs about the compressibility of water. But his apparatus and method were complicated and his results were, therefore, not universally accepted. He followed up his initial report with further experiments on water and other fluids, e.g., spirit of wine, olive oil, mercury. He confirmed his initial results and, further, found that water “has the remarkable property of being more compressible in winter than in summer,” by which he means cold water is more compressible. At 64° water was compressible only 44 parts per million; at 34° it was compressible 49 parts per million. The other fluids he tested were all less compressible in winter than in summer, i.e., when cold than when hot. He was nominated for a second Copley Medal for these experiments.[2] But before it was awarded, a committee of the Royal Society investigated his results.[3] Ferguson’s letter might give us a glimpse into Lord Cavendish’s efforts to confirm or extend Canton’s results.[4]

Ferguson was a largely self-taught instrument maker with a strong interest in astronomy and mathematics. In the 1740s and 1750s he became something of a popularizer of astronomy—he gave lectures and published books on astronomy for people who did not have training in mathematics. He also designed and made instruments. He was unsuccessful in his effort to become clerk of the Royal Society when he applied in 1763, but was soon elected fellow. In 1765 Cavendish asked Ferguson to help set up an experiment on the compressibility of fluids in the Royal Society House. Ferguson dutifully carried out the task:

Sir,
I have just been with Lord Charles Cavendish, who acquainted me of the thing contained in your Letter, and desired me to call upon you, to give you the following informations

1. To send to Mr Nairne (opposite the Royal Exchange) to desire him to send every thing that belongs to the Condenser, if finished, to the R. Society house.
2. That you sit up Shelves to hold glasses, if not already done.
3. That you provide for [sic] or five pound weight of small shot.
4. And two pound weight of Quicksilver.
5. A funnel (to be made at a Tin-Shop, with a pipe ten Inches long.
6. Conveniencies (Tea or Coffee pots) for boiling & pouring in hot water.
7. To see whether weights for weighing things in Scales are sent in.
8. A sponge.
9. Qu. whether you could assist to morrow, and how far.

I shall call upon you by and by; but must first go to a Turner’s Shop to get some things done for Lord Charles about the Experiment.
Excuse this bad paper, for I have none else in the house at present, and was loth to detain your Servant till I should send for some, who am with respect,
Sir, your most humble Servant,
James Ferguson

Friday 1 o’Clock

NB 5 July 1765 [in a different hand]
For Experiments on the Compressibility of Water & other Liquids [in a different hand]

It is tempting to see the X’s next to the items in the to-do list as evidence that Ferguson’s correspondent (who is unnamed in this letter) had completed that task. I wonder what prevented him from attending to the first and the last item? And finally, I find Ferguson’s apology for the poor quality paper fascinating for what it suggests about, inter alia, the letters Ferguson normally wrote (he implied that he typically wrote on higher quality paper), the mechanics of getting better paper (he just sent out for some), and the nature of correspondence at the time (a servant was waiting while Ferguson wrote the letter).