NATURE AT WORK. 407 



in the course of geological periods, the species becomes 

 amphibious in habit ; and then the hard struggle for 

 life in the water, with the abundance of food upon the 

 land, leads them to adopt terrestrial life. There are 

 creatures now existing, of whom it is not easy to say 

 whether they belong to the water or the land : there 

 are fishes which walk about on shore, and climb 

 trees. It is not difficult to imagine such auimals as 

 these deserting the water, and entirely living upon 

 land. 



But the development of life, in its varied aspects, 

 must always remain incomprehensible to those who 

 have not studied the noble science of geology, or who 

 at least have not made themselves acquainted with its 

 chief results. Unless the student understands what 

 extraordinary transformation scenes have taken place 

 upon the globe, all that is now land, having formerly 

 been sea, and all that is now sea having formerly been 

 land, not only once, but again, and again, and again ; 

 unless he understands that these changes have been 

 produced by the same gradual, and apparently insigni- 

 ficant causes, as those which are now at work before 

 our eyes ; the sea gnawing away the cliff upon the 

 shore ; the river carrying soil to the sea ; the glacier 

 gliding down the mountain slope ; the iceberg 

 bearing huge boulders to mid ocean ; the coralline 

 insects building archipelagoes ; the internal fires sud- 

 denly spouting forth stones and ashes, or slowly up- 

 heaving continents : unless be fully understands how 

 deliberate is Nature's method, how prodigal she is of 

 time, how irregular and capricious she is in all her 

 operations — he will never cease to wonder that allied 

 forms should be distributed in apparent disorder and 

 confusion, instead of being arranged on a regular 



