RECORD OF LIFE IN THE ROCKS. 161 



ing of it with the forms of life. In the successive ages 

 there have been variations in the vegetables and ani- 

 mals, especially the latter, which designate these ages, 

 as we learn by reading the record of the rocks. The 

 farther we go back in this record the less is the resem- 

 blance of the forms of life in the past. to those of the 

 present, and the gradual increase of this resemblance, as 

 we come down from the first dawning of life on the earth 

 to the present age, is very obvious. This great fact will 

 be developed to you in various ways as we proceed. 



244. Nature of the Evidence. You have already had 

 some glimpses of the record, and see what is the nature 

 of the evidence that it affords. You have seen that the 

 strata were formed one upon another in a certain order, 

 and that, as the material of which they are composed was 

 deposited, various remains of vegetables and animals be- 

 came mingled with it, and in the solidification made a 

 part of the rock. You see, then, how, in the midst of 

 the various disturbances of the strata, the geologist can 

 determine the relative ages of rocks by examining the 

 remains of organic substances contained in them. The 

 strata may be vertical, or may even be so far bent over 

 that the older rock may lie upon the more recent, but 

 the life-record reveals the truth ; and, farther than this, 

 the record is essentially the same in different regions of 

 the earth, so that the conclusions of geologists in one re- 

 gion may be applied in another. For example, coal is 

 found in different countries in connection with strata 

 that contain certain organic remains; for, in the construc- 

 tion of the earth, there were certain periods for the for- 

 mation of coal, and one especial period for this purpose. 

 In whatever country, then, such strata are found, it may 

 be rationally expected that coal may be found in connec- 

 tion with them. Other examples might be given of a 

 similar character, but this will suffice. 



245. Fossils. Any remains of any kind, of vegetables 

 or animals, found in rocks or in loose earth, are called 



