A. E. B.
Leeds, Jan. 28. 1851.
The Ring Dial, perhaps the most elegant in principle of all the forms of sun dial, has not, I think, fallen into greater disuse than have sun dials of other constructions. To describe, in this place, a modern ring dial, and the method of using it, would be useless: because it is an instrument which may be so readily inspected in the shops of most of the London opticians. Messrs. Troughton and Simms, of Fleet Street, make ring dials to a pattern of about six inches in diameter, costing, in a case, 2l. 5s. They are, in truth, elegant and instructive astronomical toys, to say the least of them; and indicate the solar time to the accuracy of about two minutes, when the sun is pretty high.
Formerly, ring dials were made of a larger diameter, with much costly graduation bestowed upon them; too heavy to be portable, and too expensive for the occasion. For example, at the apartments of the Royal Astronomical Society, at Somerset House, a ring dial, eighteen inches in diameter, may be seen, constructed by Abraham Sharp, contemporary and correspondent of Newton and Flamstead; one similar to which, hazarding a guess, I should say, could not be made under 100l. At the same place also may be seen, belonging to Mr. Williams, the assistant-secretary of the society, a very handsome oriental astrolabe, about four inches in diameter, richly chased with Arabic characters and symbols; to which instrument, as well as to modern ring dials, the ring dials described in "Notes and Queries" (Vol. iii., p. 52.) seem to bear relation. If I recollect right, in one of the tales of the Arabian Nights, the barber goes out, leaving his customer half shaved,
to take an observation with his astrolabe, to ascertain if he were operating in a lucky hour. By his astrolabe, therefore, the barber could find the time of day; this, however, I confess I could not pretend to find with the astrolabe in question. Ring dials, as I am informed, are in demand to go out to India, where they are in use among surveyors and military men; and, no doubt, such instruments as the astrolabe above-mentioned, which, though pretty old, does not pretend to be an antique, are in use among the educated of the natives all over the East.
Robert Snow.
I send you the particulars of two brass ring dials, seeing they are claiming some notice from your learned correspondents, and having recently bought them of a dealer in old metals.
7-16ths of an inch wide, 1 and 7-16ths over,
3-8ths wide, and 1½ over,