SCIENTIFIC NEWS. yy 



improvement of the lunar tables, which require only some 



one of sufficient coura^ to dndertake the task. 



In another paper the same astronomer has calculated the Galley's 

 /. ri 11 « L 1 1 • comet, 



perturbations of Halley s comet, which reap; earen in 1759, 



and is expected about 1835. He has found, that the at- 

 traction of the Earth will have altered the period of its re- 

 volution sixteen days. 



Having formed the plan of a grand geodetic operation Methods of 

 for joining observatories differing greatly in longitude, he a^injuihs,"^ 

 was aware of the importance of an accurate determination of 

 the azimuths to the success of his scheme, and in conse- 

 tjuence examined the advantages and disadvantages at* 

 tached to the different methods known. 



He has also determined the dip with two different needles. Dip of the 

 one of which gave 68° 47*1', the other 68" 47*4', on the 10th needle. 

 and 20th of August, I8O9. Mr. Gay-Lusi«ac had made 

 similar observations with another compass about the same 

 time; and as his dip differed sonfie minutes from that of 

 Mr. Burckhardt, thCsSe two gentlemen have agreed to repeat 

 their trials, in order to ascertain, if possible, the cause of 

 the diffi-rence. 



Mr. Biot has read a note on the observations of the pen- Figure of the 

 dulum made at the two extremities of the meridian, namely Eartii. 

 at Formentera ard Dunkirk, in company Avith Messrs. 

 Arago and Mathieu, and on the oblateness of the Earth 

 thence resulting. All these observations exhibit a surpris- 

 ing agreement with those made at Bourdeaux, Figeac, and 

 Paris, by the same gentlemen and Borda ; and give an ob^ 

 lateness differing very little from ^^-g-, which I have deduced 

 from a comparison of my arc with that of Peru. 



Mr. de Prony having been of opinion, that Mr. Ramond's Baroipetrvaifi 



cofeflficiet^T foi* barometrical measurements was too ureat '"^^^"f«* 



^ ments, 



for incouf^iderable heights, and the original coefficient of 

 Laplace better suited to them, Mr. Ramond has, several 

 titties taken the height of various places near Clefrnond- 

 Ferrand, by the barometer; and Mr. de Courbon mea- 

 sured the same heights trigonoinetrically. The heights 

 were from 300 to 6C0 yards. The differences were from 1 

 yard to 0*05. Stilt the differences betweenthf* heights as- 

 signed to Mount Cenis by Mr. Raraond and Mj*. de Prony 



remain 



