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CHAPTER XIX. 



APPLICATIONS OP THE MICROSCOPE TO GEOLOGICAL INVESTIGATION. 



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 succes- 

 sive strata of which its crust is composed, but also with regard to 

 the essential nature and composition of many of those strata them- 

 selves. — We cannot have a better example of its value in both 

 these respects, than that which is afforded by the results of Micro- 

 scopic 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. 



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

 complete preservation, are found in numerous Strata of very dif- 

 ferent 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 pene- 

 trated 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 favourable. In either case, 

 transparent sections are needed for the full display of the organi- 

 zation ; but such sections, though made with great facility when 

 Lime is the fossilizing material, require much labour and skill 

 when Silex has to be dealt- with. Occasionally, 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 laminae split-asunder with a knife, or 

 isolated fibres separated by rubbing-down between the fingers, 



