XX PREFACE TO THE 



been principally 'spent in those studies which were 

 most requisite to enable me to understand what had 

 thus been done ; and I had been in habits of inter- 

 course with several of the most eminent men of science 

 of our time, both in our own and in other countries. 

 Having thus lived with some of the great intellects of 

 the past and the present, I had found myself capable 

 of rejoicing in their beauties, of admiring their endow- 

 ments, and, I trusted, also, of understanding their 

 discoveries and views, their hopes and aims. I did 

 not, therefore, turn aside from the responsibility 

 which the character of the Historian of Science im- 

 posed upon me. I have not even shrunk from it 

 when it led me into the circle of those who are now 

 alive, and among whom we move. For it seemed to 

 me that to omit such portions of the history as I 

 must have omitted to avoid thus speaking of my 

 contemporaries, would have left my work mutilated 

 and incomplete ; and would have prevented its form- 

 ing a platform on which we might stand and look 

 forward into the future. I trusted, moreover, that 

 my study of the philosophers of former times had 

 enabled me to appreciate the discoveries of the pre- 

 sent, and that I should be able to speak of persons 

 now alive, with the same impartiality and in the same 

 spirit as if they were already numbered with the great 

 men of the past. Seeking encouragement in these 

 reflections, and in the labour and thought which I was 

 conscious of having bestowed upon my task, I have 

 conducted my history from the earliest ages of the 

 speculative world up to our own days. 



To some persons it may appear that I am not 



