150 NATURAL SELECTION vn 



its purpose so effectually. Nothing but a mind could have so 

 exactly adapted the slopes of the channels, their capacity, and 

 frequency, to the nature of the soil and the quantity of the 

 rainfall. Again, he would see special adaptation to the wants 

 of man, in broad, quiet, navigable rivers flowing through fertile 

 plains that support a large population, while the rocky streams 

 and mountain torrents were confined to those sterile regions 

 suitable only for a small population of shepherds and herds- 

 men. He would listen with incredulity to the geologist who 

 assured him that the adaptation and adjustment he so admired 

 was an inevitable result of the action of general laws ; that 

 the rains and rivers, aided by subterranean forces, had 

 modelled the country, had formed the hills and valleys, had 

 scooped out the river beds and levelled the plains ; and it 

 would only be after much patient observation and study, 

 after having watched the minute changes produced year by 

 year, and multiplying them by thousands and ten thousands, 

 after visiting the various regions of the earth and seeing the 

 changes everywhere going on, and the unmistakable signs of 

 greater changes in past times, that he could be made to 

 understand that the surface of the earth, however beautiful 

 and harmonious it may appear, is strictly due in every detail 

 to the action of forces which are demonstrably self-adjusting. 

 Moreover, when he had sufficiently extended his inquiries, 

 he would find that every evil effect which he would imagine 

 must be the result of non-adjustment does somewhere or other 

 occur, only it is not always evil. Looking on a fertile valley, 

 he would perhaps say : " If the channel of this river were not 

 well adjusted if for a few miles it sloped the wrong way 

 the water could not escape, and all this luxuriant valley, full of 

 human beings, would become a waste of waters." Well, there 

 are hundreds of such cases. Every lake is a valley "wasted 

 by water," and in some cases (as the Dead Sea) it is a positive 

 evil, a blot upon the harmony and adaptation of the surface 

 of the earth. Again, he might say "If rain did not fall 

 here, but the clouds passed over us to some other regions, 

 this verdant and highly cultivated plain would become a 

 desert." And there are such deserts over large portions of 

 the earth, which abundant rains would convert into pleasant 

 dwelling-places for man. Or he might observe some great 



