EELATIVE GEOLOGICAL ANT QUIT Y OF TREES. 143 



rocks. His first appearance, which is thought to be so myste- 

 rious, is no more difficult to understand than the appearance 

 of any other organism. He was introduced at the time when 

 the earth was ready for him. His existence on the earth, if 

 it is to be accounted for scientifically, is a question of Natural 

 History, which at present is not sufficiently advanced to ex- 

 plain the introduction of any of the forms of life which have 

 appeared at the several geological eras. He is undoubtedly 

 the noblest which has yet tenanted the earth, the crown of the 

 creation ; and as his appearance is quite a recent event, and 

 the earth has been so many ages preparing for him, the prob- 

 abilities are that it will continue to endure for myriads of ages 

 yet to come. The conviction of the constancy of Nature 

 deepens with every footstep which is taken in physical inves- 

 tigations. The system of things is perpetually changing, yet 

 the laws which govern these changes remain invariably the 

 same. When viewed by the light of the eternity that is past, 

 or seen through those vast periods contemplated in Geology, 

 the land loses its attribute of fixity and becomes as movable 

 as the ocean. These grand and more worthy views of the 

 Works of the Creator are the result of the investigations of 

 Science. It is not stating more than is strictly true, when we 

 affirm that there is physical proof in the rocky strata of our 

 globe, and the organic remains which they contain, of changes 

 which must have taken thousands of millions of years to 

 bring about, and this necessarily impresses on the mind the 

 conviction that Nature will remain subject to the same laws 

 for myriads of ages yet to come. Why should we doubt the 

 constancy of Nature through coming duration, when she has 

 left us such irresistible proof of her invariability through the 

 eternity that is past ? 



" The study of vegetable fossils," says Professor Henfrey, 

 " is far less satisfactory than that of animal remains, since, in 

 the great majority of cases, the structures most distinctive of 

 the subordinate groups of plants are formed of very perish- 

 able matter. Genera and even species of animals may be 

 recognized by bones and shells, which are of a very persistent 

 nature, and are found abundantly in stratified rocks. The 



