THE WOKLD. 



are of the utmost importance in the ej^es of geologists. If we 

 examine the successive beds of water deposits in the various parts 

 of our country we soon find that peculiar and characteristic fos- 

 sils belonging to one locality. Or if we penetrate the earth to 

 such a depth that we reach the strata, which at some distant 

 place may crop out, or appear on the surface, as explained page 

 184, we will then find the same fossil remains as would be 

 found at the surface at that distant place. The inference which 

 we naturally draw from this is, that if at different ages of the globe, 

 when the successive strata were deposited, different races of ani- 

 mals and vegetables flourished, then these fossil remains will 

 enable us to determine with something like certainty, the relative 

 ages of the strata which compose the various parts of a country, 

 for it must be remembered that the rnineralogical character of 

 most of these beds is the same, and many times no opinion 

 whatever can be formed from this. Hence these remains have 

 been appropriately termed the ** Medals of Creation," and they 

 afford to the geologist precisely the same evidence of the charac- 

 ter of the period when they existed, and were deposited, as an 

 ancient coin to the numismatist, of the character of the people, 

 and the period when it was struck. Oftentimes a single coin or 

 medal, is the sole remembrance which exists, to determine the 

 date of a great event, and so a few bones, a shell, or a tooth, or 

 track of a bird in the sand, are the sole memorials of peculiar 

 types of existence of the primeval worlds It would seem at first 

 that from the very nature of the materials which compose most 

 organic substances, that all traces of them would soon be oblit- 

 erated. It is true that the soft and delicate parts of animal and 

 vegetable organisms rapidly decay after death, yet in certain cases* 

 their decomposition is arrested, and by a peculiar process every 

 part is transformed into stone; thus, many of the most perishable 

 vegetable tissues have been preserved, and even in the anthra- 

 cite coal, which has been burned in the grate, distinct traces of 

 organic structure can be observed under the microscope. The 

 woody fibre of vegetables, the bones and teeth of animals, deeply 

 imbedded in the earth, are thus preserved in some instances with 

 wonderful accuracy and perfection. Th perishable fleshy parts 



