GOQ ARTIFICIAL STONY SUBSTANCE. 



cent, by decomposition ; but when this happens, the light 

 disengaged makes it visible the whole way, and this is in a 

 straight line. The small Jailing stars art; composed oi the 

 same Jluid, but it has been disturbed in its accent by the 

 agitation of the air; its streams have been divided, and their 

 direction changed* 



If the author has any objection to the whole, or to some 

 part of this answer to his system, I shall be giad to receive it 

 through your Journal ; but he will rind, 1 think, that it in- 

 volves many more objects of meteorology than he was aware 

 n of; as this is connected with most part of natural philoso- 

 phy, I remain, Sir, 



your most obedient servant, 



J. E. DE LUC. 

 Windsor, June the 13th, 1812. 



X. 



Remarks on an artificial stony Substance : by F. R. Cu- 



RAUDAU*. 



Solidification -Cjx. Remarkable example of the high degree of solidification 

 of water. tmt water can acquire in certain combinations is exhibited 



by the artificial stones, which form the subject of the pre- 

 sent remark. 



_ .. These stones, more than half the weight of which is water, 



Composition ■' " 



of an artificial consist also of sulphuric acid and baked clay reduced to 



Store, powder, in the proportion of one part of the former and two 



of the latter. The simple mixture of these three substances 

 affords only a solution of sulphate of aiumine : but, if their 

 mutual action be promoted, heat is soon produced, and its 

 evolution is sometimes so considerable, that the matter seems 

 incandescent. 



., . If the quantity of materials amount to 25 or 30 hundred 



Action of a . . 



l^rgd quantity weight, this beautiful phenomenon lasts above an hour. 



oi materials. Tj u { } w hat is particularly remarkable, if the matter come to 



want water at the moment when the mutual action of the 



* Joura-d« Phys. vol. LXVIII, p. 409. 



substancei 



