PREFATORY NOTICE. XI 



excite the feeling, it seemed to me the better. 

 Following my own judgment on a subject, which is 

 so perfectly original that, so far as I know, there 

 is not a book or even a page expressly on it, I 

 may be wrong and may have failed ; but even in 

 that case, I shall not feel so much humbled by 

 absolute failure in an original attempt, as I should 

 have done at inferiority in an imitation. 



The plan which I have adopted, has been to 

 throw momentary glances on those portions of 

 nature, which struck me as capable of reflecting 

 the greatest breadth and brilliancy of light ; and 

 such as I thought the most likely to induce the 

 reader (and more especially the young reader) to 

 return again to the subjects, and work out the 

 details for himself. I have studiously avoided 

 system, because it is to be wished that every one 

 should enter upon the observation of nature un- 

 fettered ; and I have also been anxious to steer as 

 clear as possible, not only of hypotheses, but of 

 theories. 



In some places I have called in the aid of num- 

 bers, to estimate causes of action which are not 

 generally estimated in that way ; but immense as 

 some of these numbers may seem, they are all 

 under what the legitimate deductions from the 

 7 



