This John Poole marine chronometer # 3364 c 1865 is now housed in a later day box most probably by Thomas Mercer. Mun C W
Mun, your chronometer has Poole's auxiliary compensation for middle temperature error applied to the balance. Some of the better makers implemented it into their chronometers. Dent, Barraud and others among them. Ralph
I have a chronometer with Poole's auxiliary that is not nearly in as nice condition as this one. Mine does have the auxiliary noted on the dial. View attachment 278933
In an article published in CLOCKS July 1984, Vaudrey Mercer investigates the errors that besets the makers of early chronometers and the diverse methods they use to overcome them. In the article John Poole's chronometer balance with auxiliary compensation was discussed. His balance prevents the rim from moving outwards to its fullest extent and hence it is suitable for exposure to extreme cold. His chronometers were much in use in the vessels sent to find the North West passage. This type of balance halves the middle temperature error and greatly reduces the error in low temperature. Mun C W
Mun, Here's another Poole, a little earlier than your's. It is serial number 3312. It started life in a brass bound rosewood box, that regretfully has lost the upper two tiers. It was my understanding the plate spotting on this one is actually associated with John Poole. I've seen the same decoration on other Poole chronometers. Naturally, chasing around the internet, I can't find any examples to support that claim. This one also has auxiliary compensation and it is not noted on the dial. Ralph
