276 fttK vvonr.h. 



great difficulty in resisting chemical changes of this kind, and of 

 preserving their original chemical nature, more particularly when 

 elevated into the atmosphere." We have already had occasion 

 to remark upon the large amount of calcareous and silicious mat- 

 ters held in solution by water, which matter has been often de- 

 rived from the percolation of that fluid through limestone districts, 

 or rocks containing felspar^ for it is well known that in the de- 

 composition of such rocks, producing the porcelain clay, an 

 enomous quantity of silex is carried off in solution. In the re- 

 gion of extinct volcanoes in France, the district of Auverge, 

 the destruction of granite is very rapid, owing to the liberation 

 of large quantities of carbonic acid. "The disintegration of 

 granite," says Lye 11, "is a striking feature of large districts in 

 Auvergne. This decay was called by Dolomieu 'la maladie du 

 granite,' and the rock may, with propriety, be said to have the 

 rot, for it crumbles to pieces in the hand. The phenomenon may, 

 without doubt, be ascribed to the continual disengagement of 

 carbonic acid gas from numerous fissures. In the Plains of the 

 Po, I observed great beds of alluvium, consisting of primary peb- 

 bles, percolated by spring water, charged with carbonate of lime 

 and carbonic acid in great abundance. They are, for the most 

 part, incrusted with calc sinter ; and the rounded blocks of gneiss, 

 which have all the outward appearance of solidity, have been so 

 disintegrated by the carbonic acid as readily to fall to pieces." 



We can now perceive how little of stability or permanancy is 

 inscribed upon the face of nature. The gilded insect which flut- 

 ters its short hour over the flowers of a day, deems its life and 

 happiness lasting, and what better are our own thoughts; we look 

 upon the earth as unchangeable, when, for ought we know, the 

 next instant may behold all our possessions swallowed up, or blown 

 into the air. We carve to ourselves costly monuments, perpetua- 

 ting the deeds of martial bravery, or the fame of a patriot, we 

 protect them from the hands of the rude by various means, but 

 a more formidable enemy, because less known, and dreaded, is 

 passing by, and silently effecting the work of desolation. Change, 

 perpetual change, is inscribed by the finger of the Almighty up- 

 on the face of everything. No art can arrest the insidious at- 



