THE MICROSCOPE IN GEOLOGY. 105 



silver on a glass slide, drop a few copper filings upon 

 it ; a brilliant arborescent form of crystallisation takes 

 place, growing rapidly as you look at it. This is an 

 interesting case of affinity. The nitric acid imme- 

 diately combines with the copper, and the silver 

 appears in the metallic state. 



CHAPTER X. 



THE MICROSCOPE IN GEOLOGY. 



THE geological student will gather a vast amount of 

 information by means of the microscope. He will be 

 able to determine the nature of the minute animal and 

 vegetable remains that are found in various strata ot 

 the earth's crust, as well as the composition of many 

 of the strata themselves. Huge mountains have been 

 shown, by the aid of the microscope, to be composed 

 of countless millions of minute organisms, such as 

 Diatomacecz, Foraminifera, &c. " Startling and almost 

 incredible as the assertion may appear to some," as 

 Mr. Hogg truly observes, " it is none the less a fact 

 established beyond all question by the aid of the 

 microscope, that some of our most gigantic mountain 

 ranges, such as the mighty Andes, towering into space 

 25,250 feet above the. level of the sea, their base occu- 

 pying so vast an area of land, as also our massive 

 limestone rocks, the sand that covers our boundless 

 deserts, and the soil of many of our wide extended 

 plains, are principally composed of portions of in- 

 visible animalcules. And, as Dr. Buckland truly 

 observes, ' The remains of such minute animals have 

 added much more to the mass of materials which com- 

 pose the exterior crust of the globe than the bones of 

 elephants, hippopotami, and whales/ " In some cases 



