crystallhed Bodies contained in Lava. 45 



have acted hive undergone an incomplete fusion only, and 

 that their crystals remained untouched in the middle of their 

 fluid paste, are obl!a;ed to have recourse to a multitude oF 

 suppositions, in order to explain the state in which lavas 

 are when cooled." 



These naturalists have recourse to no such supposition. 

 Nothing changes the form or the nature of lava after it has 

 cooled. The foreign substances which it contains in its 

 burning paste, remain in the same form ; no changes are 

 produced, the fire of the volcanoes not having had power 

 sufficient to fuse or alter them. I have given a great num- 

 ber of examples of this. 



I shall call on this occasion to the recollection of my 

 readers, the idea T presented in my former memoir, upon the 

 probable state in which the subterranean volcanoes were 

 from whence the lava issued. We see that, in order to reduce 

 the rocks and the minerals to fusion, they must be broken 

 into pieces : nevertheless there are no stampers or grinding 

 machines in the strata where the lavas take their origin, and 

 the volcanic fires, any more than those of cur furnaces, can- 

 not melt rocks in large masses. One would thmk, therefore, 

 that in such beds the chemical affinities may be exercised, and 

 form isolated and grouped crystals which remain enveloped 

 in the matter in fusion. How does this fusion take place, 

 and whence proceed the fires th.it produce it? We see from 

 the various emanations that sulpliur is the chief ingredient, 

 and that iron enters into ihe mixture ; that the marine acid 

 and sal-ammoniac also form parts of the mixture : but uhat 

 circumstance, what combination is requisite to excite the 

 fermentation which produces the fires, the fusions, and the 

 other volcanic phseuomena ? Upon this we can only form 

 conjectures, some of which may approach nearer to the truth 

 than others. But as all the means in our power can neither 

 hinder nor produce any thing, it is of little importance to 

 know upon what our conjectures are loundcd as to the origin 

 of these fires, and the manner in which they act. What is 

 essentially reipiisite, is, to take care not to gis'e them a wider 

 influence, nor to attribute more action to them, than they 



reaUy 



