viii PREFACE. 



sciences ought to be too evident to require demonstration. 

 Geology and mineralogy render daily services to industry, 

 by enabling us better to explore the wealth buried in the 

 bowels of the earth ; Botany makes us acquainted with the 

 plants, so varied and so beautiful, which supply our wants 

 in magnificent prodigality ; Zoology gives a knowledge 

 of those animals which produce wool, silk, and honey, and 

 those that assist us in our toils with their strength, as well 

 as of those which, instead . of being useful to us, destroy 

 our crops. How important a guide natural history may be 

 made to agriculture, the great pursuit in the United States ! 

 Besides, let us remember the long list of diseases by which 

 the human machine is afflicted, and bear in mind the fact 

 that the practice of medicine is blind in action when it does 

 not rest on a scientific knowledge of the nature of man. 



The practical importance of the study of natural history, 

 we repeat, requires no proof, and must be felt, no matter 

 what may be our career. But its influence does not stop 

 here ; the influence it can be made to exert over our facul- 

 ties themselves, is worthy of the most serious attention. 

 In fact, the natural sciences, by reason of the routine sys- 

 tem peculiar to them, accustom the mind to go back from 

 effects to causes, and at the same time invariably submit 

 results deduced from preceding observations to the test of 

 new facts ; their study leads to speculations of the most 

 elevated character, but never leads the imagination astray, 

 because it always places material proof alongside of theory. 

 And beyond any other- pursuit, natural history exercises 

 the mind in habits of method, a part of logic without which 

 every investigation is laborious, and every exposition ob- 

 scure. 



Natural History ought to constitute one of the elements 

 of every system of liberal education ; but it is not neces- 

 sary that every young man should be a naturalist. To 

 become a proficient in a science so vast in its scope, would 



