INTRODUCTION. XX111 



any debasing mixture; it tends to enlarge 

 and harmonize the mind, and to elevate it to 

 worthy conceptions of Nature and its Author : 



The men 



Whom Nature's works can charm, with God himself 

 Hold converse ; grow familiar, day by day, 

 With his conceptions ; act upon his plan, 

 And form to his the relish of their souls." 



AKENSIDE. 



In the following Treatise it has been my 

 endeavour to combine, as much as possible, 

 the profitable with the instructive and amu- 

 sing ; in seeking which object, I have endea- 

 voured to clear the ground before me, of the 

 wild-flowers of conjecture and hypothesis, 

 with-which the fecundity of the human ima- 

 gination has strewed it, and to substitute in 

 their place the less showy but more useful 

 products of experiment and rational deduc- 

 tion, the growth of which it should be the 

 object of every labourer in the field of science 

 to promote. Always bearing in mind that 

 false theories often lead to erroneous prac- 

 tices, I have carefully abstained from an in- 

 dulgence in theory of a merely speculative 

 kind, and confined myself simply to offering 



