Scientifie News, Accounts of Booh, CBc 8*> 



SCIENTIFIC NEWS, ACCOUNTS OF BOOKS, STc. 



BOARD OF LONGITUDE OF FRANCE. 

 Prize of JJlrommy. 



X HE tables of the moon are equally interefting to aftronomy and navigation. The 

 moft celebrated geometers have afllduoufly cultivated the theory on which thefe tables are 

 founded. The moft important care of the practical aftronomer is to obferve all the 

 motions of this planet, without which there would be no truth in geography, and which 

 furniflics the navigator with the fureft means of knowing the fituation of his veltel, of 

 dlreding his courfe, and fafely arriving at any determined fpot of the globe. In propor- 

 tion as the Newtonian theory has been inveftigated, and the greater the pcrfeftion to 

 which inftruments and the method of obferving have been brought, in the fame proportion 

 have the lunar tables been improved. Mayer, joining his own refearches to thofe of the 

 geometers of his time, and making choice of thofe obfervations which were the moft to 

 be depended upon, fucceeded in forming tables which, by fubfequent comparifon with 

 nearly twelve hundred unpubliflied obfervations, agreed with the moft aftonifhing pre- 

 clfion. Mafon, under the diredlion of Dr. Mafkelyne, rendered them ftill more perfedl, 

 by reftoring feveral equations which had been omitted, though pointed out by Mayer, 

 and by modifying the coeflicients of all the others. 



In fpite of all this care, thefe tables, which in the middle of the century were fo accu- 

 rate, began progreflively to lofe their exaflnefs. On recurring to the theory, the caufe of 

 the error and its remedy were feen. The prize memoirs, which two years ago were fent to 

 the National Inftitute, and were publifhed in the feflion of the fifteenth of Germinal laft, 

 have placed in the cleareft point of view both the neceflity and precife quantity of the 

 •quations lately difcovered for the motions of the apogee' and the node. Aftronomers were 

 not then invited to employ themfelves on all the elements which compofe the lunar tables ; 

 the labour was too much difproportioned to the time appointed for the concurrence. 

 One fuccefsful difcovery often gives the wi(h and frequently the means of making another. 

 That which has been fo happily performed, has proved the pofTibility of doing ftill 

 more, and of procuring for aftronomy lunar tables of greater precifion as well as durability. 

 Nothing more remains after the fixation of the epochs, the fecular movements, and their 

 inequalities, than to difcufs anew, by comparifon with a great number of accurate ob- 

 fervations, the precife quantity of the different equations which enter into the calculation 

 of the moon's place. 



This is the problem which the Board of Longitude of France now propofes for 

 folution to the aftronomers of all countries. The conditions are : 



Vol. IV. — October 1800. Uu i. To 



