CHAPTER XIX. 



APPLICATIONS OF THE MICROSCOPE TO GEOLOGICAL INVESTIGATION. 



441. THE utility of the Microscope is by no means limited to 

 the determination of the structure and actions of the Organized 

 beings at present living on the surface of the earth ; for a vast 

 amount of information is afforded by its means to the geological 

 inquirer, not only with regard to the minute characters of the 

 many Vegetable and Animal remains that are entombed in the 

 successive strata of which its crust is composed, but also with 

 regard to the essential nature and composition of many of those 

 strata themselves. We cannot have a better example of its 

 value in both these respects, that that which is afforded by the 

 results of microscopic examination of lignite or fossilized wood, 

 and of ordinary coal, which there is every reason to regard as a 

 product of the decay of wood. 



442. Specimens of Fossilized Wood, in a state of more or less 

 complete preservation, are found in numerous strata of very 

 different ages, more frequently, of course, in those whose 

 materials were directly furnished by the dry land, and were 

 deposited in its immediate proximity, than in those which were 

 formed by the deposition of sediments at the bottom of a deep 

 ocean. Generally speaking, it is only when the wood is found 

 to have been penetrated by silex, that its organic structure is 

 well preserved; but instances occur every now and then, in 

 which penetration by carbonate of lime has proved equally favor- 

 able. In either ease, transparent sections are needed for the 

 full display of the organization ; but such sections, though made 

 with great facility when lime was the fossilizing material, require 

 much labor and skill when silex has to be dealt with. Occasion- 

 ally, however, it has happened that the infiltration has filled the 

 cavities of the cells and vessels, without consolidating their walls ; 

 and as the latter have undergone decay without being replaced 

 by any cementing material, the lignite, thus composed of the 

 internal "casts" of the woody tissues, is very friable, its fibres 

 separating from each other like those of asbestos ; and their 

 laminae split asunder with a knife, or isolated fibres separated by 

 rubbing down between the fingers, exhibit the characters of the 

 woody structure extremely well, when mounted in Canada 



