Geological Society of France for 1847. 163 



ject. In chemical composition this paste contained silica in the same 

 proportion as in the isolated crystals of labradorite, and in all the 

 varieties less alumina, soda, and potash, and more iron, manganese, 

 and magnesia, with sometimes more, and sometimes less, water and 

 lime. The spilite of Fauconey, a vesicular rock, was found upon ana- 

 lysis to be nearly of the same composition as the base of the Belfahy 

 porphyry. 



In conclusion, M. Delesse points to the approximation which these 

 researches on the Vosges melaphyres establish between them and 

 basalts. The base of the two rocks is the same, being labradorite, 

 and they likewise contain augite and oxidulated iron in common ; 

 both also contain water. The differences consist chiefly in the greater 

 or less proportion of bases in the constituent labradorite. Thus soda, 

 potash, and water form a notable part of the labradorite of the mela- 

 phyres, while these bases diminish and even completely disappear as 

 the rock approaches to greenstones, basalts, and modern lavas. They 

 are replaced by lime, which then becomes the dominant base. 

 {^To he continued in our next Number.) 



On tlie Decomposition and partial Solution of Minerals, Hocks, 

 ^c, by Pure Water, and Water charged with Carbonic Acid. 

 By Professor W, B. Rogers, and Professor E. E. Rogers, 

 of the University of Virginia. * 



The present brief notice is designed as a mere abstract of 

 the more prominent results of our investigations in this very 

 interesting field of experiment. The facts accumulated dur- 

 ing upwards of four months of laborious research, have be- 

 come so voluminous as to acquire further time for throwing 

 them into a shape suited to a detailed publication ; but we 

 trust that the heads of our inquiry here presented, will suf- 

 fice at present-to indicate the scope of the experiments, and 

 the great intei'est of many of the determinations, especially 

 in their bearing upon the chemisti'y of geology, the forma- 

 tion of soils, and the nutrition of plants. 



It is matter of surprise that so little has hitherto been done 

 to determine, by actual experiment, the solvent porver of water, 



* Communicated for this Journal (Professor Silliman's American Journal of 

 of Science and the Arts) by the authors, in advance of a more extended me. 

 moir on the same subject, which will appear in a future number. 



