Geology and Biology 83 



its activities, in as strict a sense as are warmth and the move- 

 ments and products of respiration the activities of an animal. 

 The phenomena of the seasons, of the trade-vpinds, of the Gulf 

 Stream, are as much the results of the reaction between these 

 inner activities and outward forces, as are the budding of the 

 leaves in spring, and their falling in autumn the effects of the 

 interaction between the organisation of a plant and the solar 

 light and heat. And, as the study of the activities of the li\ang 

 being is called its physiology, so are these phenomena the sul> 

 ject matter of an analogous telluric physiology, to which we 

 sometimes give the name of meteorology ; sometimes of physi- 

 cal geography, sometimes that of geology. Again, the earth 

 has a place in space and time, and relations to other bodies in 

 both these respects, which constitute its distribution. This 

 subject is usually left to the astronomer ; but a knowledge of 

 its broad outlines seems to me to be an essential constituent of 

 the stock of geological ideas. 



"All that can be ascertained concerning the structure, suc- 

 cession of conditions, actions, and position in space of the 

 earth, is the matter of its natural histor}-. But, as in Biology, 

 there remains the matter of reasoning from these facts to their 

 causes, which is just as much science as the other, and indeed 

 more ; and this constitutes geological aetiology. 



" Having regard to this general scheme of geological know- 

 ledge and thought, it is obvious that geological speculation 

 may be, so to speak, anatomical and developmental specula- 

 tion, so far as it relates to points of stratigraphical arrangement 

 which are out of reach of direct observation ; or, it may be 

 physiological speculation so far as it relates to undetermined 

 problems relative to the activities of the earth ; or, it may be 

 distributional speculation, if it deals with modifications of the 

 earth's place in space ; or, finally, it will be aetiological specu- 

 lation if it attempts to deduce the history of the world, as a 

 whole, from the known properties of the matter of the earth, 

 in the conditions in which the earth has been placed." 



Huxley then proceeded to shew that uniformitarian- 

 ism and catastrophism had neglected this last and most 

 important branch of geology, the attempt to trace the 



