XXVI] 



HERBERT SPENCER 



25 



had had a h'ttle private conversation, we would go into the 

 drawing-room where there was music, and Spencer would 

 sometimes play on his flute. On remarking to him one day 

 that I wondered he could live among such unintellectual 

 people, he said that he had purposely chosen such a home in 

 order to avoid the mental excitement of too much interesting 

 conversation ; that he suffered greatly from insomnia, and 

 that he found that when his evenings were spent in common- 

 place conversation, hearing the news of the day or taking 

 part in a little music, he had a better chance of sleeping. 



In the autumn of 1867 I read the Duke of Argyll's 

 "Reign of Law," and though I found much that was 

 erroneous and weak in argument, I thought his discussion 

 of the mode of flight in birds, founded largely on personal 

 observation, was very good ; in fact, the best I had seen. 

 Spencer had also read this, and differed from me, thinking 

 that important parts of the duke's theory of flight was not 

 true, because they would not apply equally to bats ; and we 

 had quite a discussion on the subject. The next day, after 

 thinking the matter over, I wrote him a long letter of eight 

 pages, trying to show that the general principles of flight 

 in birds, bats, and insects were the same ; but that in birds 

 there were additional special adaptations that render their 

 flight more perfect, and their power of motion through the 

 air, under adverse conditions, more varied and more complete. 

 The duke, dealing with birds only, had dwelt most on these 

 special adaptations (chiefly, if I remember, the beautiful 

 overlapping and movements of the separate feathers increas- 

 ing resistance during the downward, and decreasing it during 

 the upward stroke) which did not exist in bats or in insects. 

 I also showed that although this adaptation was absent in 

 the wings of insects, the general form and movements of the 

 wings were similar and produced similar, but not identical 

 results. In his reply he admitted the accuracy of my 

 description of the flight of insects, but made the following 

 remark in furtherance of his former objection as regards the 

 duke's account of the flight of birds : " If you will move 

 an outstretched wing backwards and forwards with equal 



