Sgct.VIII.] Astronomy. 83 



is due the honour of contributing much toward the 

 perfection of the plan, and of introducing it into 

 general practice. 



Another method of finding the Longitude, by 

 observations on the Eclipses of Jupiter's moons, 

 though practised as early as 1688, has yet been 

 much improved during the period under discussion. 

 For these improvements, which are chiefly found- 

 ed on the superior extent and accuracy of modern 

 tables, -we are indebted principally to Drs. Bradley 

 and Pound, M. Cassini the younger, Mr. Wargen- 

 tin, and Tvl. Delambre, the tables of the last of 

 whom have been generally adopted in man}' of the 

 late nautical almanacks. A third mode of deter- 

 mining the Longitude, by well regulated Time- 

 keepers, is almost wholly a production of the last 

 age. For although some attempts of the kind 

 were made in the preceding century, nothing elfec- 

 tual was done until 1714, when Henry Sully, an 

 Englishman, published a small tract at Vienna, on 

 the subject of watch-making, and annouAced some 

 improvements in the art, with a view to the Lon- 

 gitude, which were said to be valuable, and attend- 

 ed wath success. This plan, however, was after- 

 wards bro'ught much nearer to perfection, by the 

 ingenious and persevering labours of John Harri- 

 son, also of England, w4io, in 1726, produced a 

 time-keeper of such uncommon accuracy as not to 

 err above one second in a month, for ten years 

 together. Watches of a similar kind, which have 

 proved of great utility to navigators, were also 

 formed soon after Harrison*s^ by Kendal, Arnold, 

 and others of Great Britain, and by Ic Roy, Ber- 

 thoud, and several other distingnislied French 



G2 



