Chronometer no. 524 by Thomas Earnshaw

Catalogue description — Royal Museums Greenwich

Plain, two-tier Earnshaw-style mahogany box with open dovetail construction and sliding lid and ypical Earnshaw-type, one-day full plate fusee movement. This chronometer is referred to in one of the testimonials published by Thomas Earnshaw in his Appeal to the Public [FN: Earnshaw I, p.249]. The letter, which was from Chief Officer John Stevens, of the East India Company ship Elphinstone, reads: I am ashamed of having so long neglected to write to you, concerning your timekeeper No. 524, which I had on the last voyage with me. I have had many under my care, and of different makers, but never had one that could in any way be brought in competition with the one above mentioned: it is to be observed it is the first box-chronometer of yours which I ever had; the rate you gave me of it was losing two seconds daily, which rate was allowed on it for the greatest part of a long voyage; but I found that it did alter its rate a little, and in one passage it had increased to three seconds nine tenths per day, which I believe to be its greatest loss at any time on the voyage; and I have good reason to think it might be depended upon not to alter its rate more than the little difference I have above stated from 2” to 3.9” per day, and if the mean rate had been allowed for the whole voyage, it would have given the longitude true within twenty minutes of a degree at any time; but I do not think it ever differed so much from the truth as I have above supposed, as in a long passage of eighty days it made the land within thirty minutes of a degree, a degree of accuracy the most sanguine makers could scarce expect to be equalled, the most enthusiastic friends to timekeepers could never expect to be exceeded. I must further beg leave to observe, that as I seldom omitted an opportunity of observing lunar distances, I always had an opportunity of judging that there was no material variation at any intermediate time on this passage. If it can be of any service to you to produce the observations upon which the above remarks are founded, I shall be glad to do it, in justice to your merits, and for the benefit of the public at large, who are so deeply interested in the advantages arising from your extraordinary exertions and discoveries. It is not known for how long Stevens kept the chronometer, and its subsequent history is unknown up to the 1960s. The chronometer was bought by the collector Robert Foulkes from the horologist Gerald Grundsell in August 1967