EXPERIMENTS ON MOLYBDEXA. ]2l 



ever be more perceptible in the refraction, which would oc- I-nnar refrac- 

 casion an alteration in the apparent place of a star about to ^^""' 

 be eclipsed, and which would amount, in the case of the 

 Earth's atmosphere, to 66 minutes. But the refractive den- 

 sity of the lunar atmosphere would vary nearly as the 134th 

 root of the distance, instead of the 7th ; and the deviation, 

 instead of 66 minutes, would become 13' 50", one 1200th of 

 which would be only /^ of a second, which would still be 

 imperceptible; although in two or three centuries, since the 

 rarefaction would increase at first as the square of the time, 

 it might perhaps be discoverable; and this would be consi- 

 derably sooner than the decrease of the moon's apparent dia- 

 meter could be observed. It is however scarcely probable, 

 that so slow a rate of diminution could have reduced the lunar 

 atmosphere from a density equal to that of the terrestrial at- 

 mosphere, to its present state, in the course of 10,000 years. 

 I am, Sir, i 



Your very obedient servant, 

 167V%, 1808. HEMEROBIUS. 



Experiments on Moli/bdcena: ii/ Christian Frederic Bu- 

 CHOLZ. Translated from the German*. 



T is near thirty years ago, that the immortal Scheele Metal 



lybdena d 

 vored by 



iscb- 



I 



discovered in molybdena, as it was then called, a peculia 

 metallic substance, many of the properties of which he Scheelt 

 made known, as well as its action on several other sub- 

 stances. 



Several able chemists, as Pelletier, Heyer, Ilsemann, Since examin- 



Richter, Hielm, Klaprotb, Ruprecht, and others, have ^'^ ^^ several, 



J ,1 ... . , , . but our know- 



smce turned their attention to the same subject : but the ledge of it im- 



knowledge we have acquired from their labours is by no Perfect. 



means proportional to the number of chemists, who have 



examined it, and the time that has elapsed since the disco- 



* Journal des Mines, No. 106, p 241, Th- original was published 

 in Creirs Journal, Vol, IV, 1S05. 



very 



