1S4 Kew Fulminating Powder, 



into contact^ and end to end^ the two images of the main 

 mast, and you will know how many lengths of that mast 

 you are distant ffom the vessel. At land, you observe the 

 images of a corps of the enemy, and place these images in 

 such a manner that the feet of the one may sland on the 

 btads of the other; and if you estimate the mean height of 

 a soldier at five feet ten inches, the telescope will show how 

 many times that quality is contained in the distance you 

 are trom the enemy. — This short explanation sufficiently 

 proves of what utility this instrument may be, and which 

 \vould even be interesting were it only an object of mere 

 curiosity. Experiments on this subject were repeated at 

 Saint-Cloud on Tuesday, the 31st of May, before the 

 First Consul, who ordered several telescopes of this kind to 

 be constructed. This discovery may be of great use also to 

 astronomy. C. Rochon has already employed it to mea- 

 sure the diameters of Mars, Jupiter, and Saturn, At first 

 be was not able to apply it to toe sun and moon, the dia-r 

 meter cf which is aoout 30', because the angle of refracr 

 tion is only 20' ; but Rochon and Torelli de >Jarcy, by cut- 

 ting the cry'stal in an ingenious maimer, were able to dou- 

 ble and even to triple the angle of refraction. There is 'no 

 planet, therefore, the diameter of which cannot be mea- 

 sured in this manner, provided it be sufficiently luminous j 

 for it is evident that the two images are necessarily weaker 

 and fainter than one imege would be. There is no incour 

 venience of this kind in regard to the moon and sun, which 

 have si V ays too much light ; and one of these prisms is 

 going to be adapted to the best telescope in the national 

 pbservatory. 



XXXI, Jnielligence and Miscellaneous ^riickSf 



NEW FUL^IINATING PQWDEB. 



Jl ROFfissoR Prqust, jn 3L letter to A. I. C. Delametherie, 

 savs : " I have made in the course of my lectures an ex- 

 periment which had almost been attended v/ith serious con- 

 sequences tp my auditors. It i§ not exaggeration, perhaps, 

 to say, thq,t a mixture of oxygenated muriate* with arse- 

 nic takes fire v^.th the rapidity of lightning. I am ac-r 

 customed to compare the duratiqr> of different kinds pf 



* riv jciLT-l de Physique, from whicli we have taken thi| notice, 

 4oej not say what ux yg«stated m^riate was employe^. 



powder 



