338 Astronomy. [Lecture 21. - 



Subsequent admeasurements carried on upon 

 a large scale, and with great accuracy, in Eng- 

 land and Scotland, by Roy, Mudge, and Colby ; 

 in France by Delambre, Mechain, Arago, &c. ; 

 in Denmark by Schumacher ; in Lapland k by 

 Swanberg ; and in India by Lambton. Though 

 they are attended by certain minute irregularities, 

 all tend to confirm the general result that the 

 axes of the earth are in about the ratio of 304 

 to 305. 



Experiments on the pendulum in different 

 places, as, by Bouguer at the equator, Campbell 

 at Jamaica, Ciscar at Madrid, Borda and Biot 

 at Paris, Whitehurst and Kater at London, Biot 

 at Leith and Unst, Dr. Olinthus Gregory at 

 Woolwich, and in Balta Isle, Zetland, and Lord 

 Mulgrave at Spitsbergen ; all prove, generally, 

 that the equatorial axis exceeds the polar axis. 

 A synoptical account of the results, agreeably to 

 this latter method, is given in Tilloch's Philoso- 

 phical Magazine for June, 1819. 



There is nothing of more importance to a naval 

 people than the power of ascertaining the Longi- 

 tude at sea. This problem is ultimately resolva- 

 ble into that of knowing the precise hour at the 

 place where the mariner is, and the precise hour 

 at any other place the longitude of which is well 

 ascertained London, for instance. It is easy to 

 find the hour at any place where the mariner may 

 happen to be, by observing the height of the sun 

 or of any fixed star ; and observations on the 



