SCIENTIFIC NEWS. 339 



ractcristic epochas of their existence from the geologic 

 proportions of the successive or gradual strata in which 

 they take their origin, in order to establish upon those 

 data a better judgment than has heretofore been made 

 concerning the revolutions our globe may have been 

 subjected to with regard to the animal kingdom. It will 

 therefore be necessary, for the accomplishment of this 

 purpose, to endeavour to collect into determinate spe- 

 cies the animal skeletons at present come to our know- 

 ledge, to shew the identity and the diiferences of these 

 skeletons with respect to living animals ; and lastly, to 

 assign to the species, considered as extinct, the rank 

 which they ought to hold in the natural history of the 

 animals still existing on the face of the earth. 



Planetary Epocha, 

 ■ M. de Lalande received, in the month of April last, planetary cpo* 

 an anonymous letter, from Franckfort, in which it was cha of 280,00* 

 said that a German of high reputation in several sciences y^*'** 

 discovered, fifty years ago, a remarkable period of 

 280,000 years for the return of the six planets to the same 

 point of the heavens, and his opinion thereon is re- 

 quested to be given in the Magazin Encyclopedique of 

 M. Millin. The number of revolutions found by the 

 German astronomer for each of the planets have been 

 reduced into seconds by Lalande from the revolutions as 

 at present known, and are as under : 



Mercury 1162577 8836135098921. 



Venus 455122 8835595689448. 



Earth 280000 8835940680000. 



Mars .. 148878 8835946519500. 



Jupiter .... 23616 8835946544448. 



Saturn 9516 8835946558608. 



M. Lalande remarks, that these numbers differ so little ^ 



that the deviation from the same precise number of se- 

 conds in each sum of revolutions is not greater than the 

 uncertainty in the known durations of those revolutions. 

 He therefore considers the return of the planets in 280,000 

 years as a curious result, and is desirous of knowing the 

 name of him who had the courage to make such long 

 calculations. 



