French Kaii07ial Iiifiilutc. 183 



mafs confifts of oxide of iron, magncfia, and filcx. The 

 opinion of Dr. Chladni, that thele meteoric productions 

 are fragment? of fire balls \vhich have hurll, may be confi- 

 dered a^s fullv eftahliihed. Real native iron from the mines 

 of KamsdorfTi? diftintruiflied from the meteoric iron by not 

 containing any nickel^ and bv containing a mixture of cop- 

 per-lead. 



FRENCH NATIONAL INSTITUTE. 



Account of the labour? of the Mathematical and Phyfical 

 Clafs during the firll quarter of the year 11. 



Mathematical part, read by C. Lacroix. 



ASTRONOMY. 



Ohfcrvat'ions on the Tranfit of Mercury oi-er the Su?i's Difc, 

 November 9, 1802. 



If the theorv of attraction, aided by the powerful means of 

 analvfi*, has enabled aftronomers to give, alnioft at onc9, to 

 the tables of the planets, and particularly to thr)fe of the moon 

 and fun, a decree of cxaftnefs far fuperior to that to which 

 thev could have been carried by the efforts of obfervers alone 

 during a long feries of ages, time has not, on that account, loft 

 its ricrht to Ihe perfection of thefe refults deduced from the 

 mcafurenient of its duration. Alironomers therefore, always 

 attentive to the fpeftacle of the heavens, never fuller to cfcapc 

 but with regret opportunities of obferving the fimpleft and 

 inoft frequent pha?nomena, becaufe they know that, however 

 precife they mav be for the moment at which they are af- 

 fiiined, aftronomical determinations have continual need of 

 being redified : with much more reafon, therefore, they are 

 anxious to take advantage of thofe circumftanccs where the 

 pofition of the planets is Ids afieCted by the combination of 

 their own motion and that of the earth. Such in regard to 

 Mercurv arc his tranfits over the difc of the fun. 



The firft of thefe phtenomena prcferved in the annals of 

 afironomy was obferved in 163 r, at the college of France, by 

 Gaflendi, one of the moll illultrious profcilbrs of that cele- 

 brated fchool. Since that time great attention has been paid 

 to this phasnomenon ; and the obfervalions of thefe tranfits, 

 which f(;llo\veach other pretty rapidlv, have been multiplied. 

 C. Lalande has employed himfelf in collecting and examin- 

 ing them with a care and afliduity for which he has been re- 

 warded bv the jierfeCtion lie has thence been able to give to 

 his tables of Mercurv. After having fucccflivcly correCled 

 each clement, he waited for a confirmation of them by tlie 

 N 4 tranfit 



