438 THE PRINCIPLES OF SCIENCE. [CH. xix. 



v.pecies. It might as well be argued that no geological 

 changes are taking place, because no new mountain has 

 risen in Great Britain within the memory of man. Our 

 actual experience of geological changes is like a point in 

 the infinite progression of time. When we know that rain 

 water falling on limestone will carry away a minute 

 portion of the rock in solution, we do not hesitate to 

 multiply that quantity by millions, and infer that in 

 course of time a mountain may be dissolved away. We 

 have actual experience concerning the rise of land in some 

 parts of the globe and its fall in others to the extent of 

 some feet. Do we hesitate to infer what may thus be done 

 in course of geological ages? As Gabriel Plattes long ago 

 remarked, " The sea never resting, but perpetually winning 

 land in one place and losing in another, doth show what 

 may be done in length of time by a continual operation, 

 not subject unto ceasing or intermission." l The action of 

 physical circumstances upon the forms and characters of 

 animals by natural selection is subject to exactly the same 

 remarks. As regards animals living in a state of nature, 

 the change of circumstances which can be ascertained to 

 have occurred is so' slight, that we could not expect to 

 observe any change in those animals whatever. Nature 

 has made no experiment at all for us within historical 

 times. Man, however, by taming and domesticating dogs, 

 horses, oxen, pigeons, &c., has made considerable change 

 in their circumstances, and we find considerable change 

 also in their forms and characters. Supposing the state of 

 domestication to continue unchanged, these new forms 

 would continue permanent so far as we know, and in this 

 sense they are permanent. Thus the arguments against 

 Darwin's theory, founded on the non-observation of natural 

 changes within the historical period, are of the weakest 

 character, being purely negative. 



1 Discovery of Subterraneal Treasure, 1639, p. 52. 



