Rare vernier sextant made by James Thomson Bottomley (1845-1926). Bottomley was an independent London instrument maker and known for his later partnership in the instrument maker Kelvin Bottomley & Baird Ltd. There is an interesting association that existed before this firm was formed. Bottomley's uncle, William Thomson was the Professor of Natural Philosophy at Glasgow University. He was the silent partner in the firm James White, a Glasgow optical instrument maker who made instruments, especially compasses, to Thomson's designs, as well as apparatus for the University. Thomson, knighted as Baron Kelvin of Largs in 1892, became open about his commercial interests from this date and formed the firm Kelvin & James White Ltd. Bottomley joined this company in 1900 and in 1913 the firm became known as Kelvin Bottomley & Baird Ltd.
It is probable that the pre-1900 Bottomley produced instruments were to Thomson's designs  and that perhaps Thomson also had a silent partnership with Bottomley, similiar to his arrangement with James White.
Bottomley sextants are finely crafted and uncommon.
This instrument has the original japanned finish. The vernier scale is silvered on a brass base, lettered Bottomley London. Undated but late nineteenth century.
In a mahogany case. Complete with the full compliment of four telescopes.
The instrument in working order.