So Volcanoes. 



In the month of January laft year, a flight {hock of an earth- 

 quake was experienced in the whole of the weft of France, 

 from Rouen to Bourdeaux. The fame di{lrl(^ experienced 

 alfo a violent agitation in 1755, '^^ ^'^^ *^'^^^^ °^ ^^^ earthquake 

 which deftroyed Lifbon. No extinguiflied volcanoes, how- 

 ever, are known in that diftrift except in the neighbourhood 

 of Treguier. 



On the 29th of Prairial there was a terrible earthquake at 

 Acapulco : whole diflri<Sls were convulfed, and the port was 

 filled up. 



Salmon has given a beautiful memoir on the origin of 

 volcanic bafaltes. Some, among whom are the greater part 

 of the French naturalifts, have confidered them as the pro- 

 duftion of fufion by fire. Others, fuch as the celebrated 

 Werner, are of opinion that bafaltes has been depofited by 

 water. Salmon undertakes to reconcile the two hypothefes, 

 and afTcrts, that they have been produced by an aquofo-ig- 

 neous liquefaftion. Water reduced to vapour, for example, 

 in Papin's digefter, acquires a great degree of heat, capable 

 of fufing various fubftances which require a ftrong" heat to 

 be reduced to that ftate. All volcanic vapours and all fpi- 

 racles contain a great quantity of water. 



He is of opinion that feveral fubtlances contained in ba- 

 faltes, fuch as feld-fpar, augite, hornblende, zeolithes, and 

 mica, have been enclofed in it accidentally while it was 

 liquid. But he thinks that there are feveral others, fuch 

 as leucites, which have been fufed with the bafaltes, which 

 have afterwards cryRallifi-d apart, and been feparated from 

 the mafs by different laws of affinity. 



Buch entertains the fame opinion. He has no doubt that 

 leucite has cryftallifed in the mafs of the bafaltes at the mo- 

 ment of its liquidity. The portions of hornblende or of ba- 

 faltes, found in the centre of feveral cryftals of leucite, feem 

 to tliefc naturalifts a convincing proof of their opinion. 

 [To be comiuued.] 



i^EW 



