PREFACE. ix 



to degenerate into mere extractive matter. Every worker 

 and thinker is allowed to speak for himself, and there 

 are few allusions made to the opinions of any, however 

 eminent, who has not himself laboured on the subject. 

 In the court of science every man is his own best 

 witness ; by using description instead of quotation we 

 employ advocates who bandy about the meaning, until 

 at last it can nowhere be found. We cannot be too 

 careful of the fame of the absent, were it merely to 

 protest against the loud assertion of self, which is so 

 easy for those who are present, even when their only hope 

 of fame lies in that two-edged truth, that "a living dog 

 is better than a dead lion." 



ERRATA. 



Near bottom of page 77, the inverted commas should begin, ** For one is not 

 the same." 

 Page 79, for air and matter^ read air and water. 

 Page 251, for John Qough W., read ffeiiry Hough W. 



