674 W- M- DAVIS 



currents from the drift of graptolite stems; and with the glaciologist, 

 who is asking the astronomer and the physicist whether one or the 

 other of them can best account for the Pleistocene ice-sheets. 



Not only do the different parts of earth science thus connect with 

 one another, but, as the last illustration showed, they interlace most 

 interestingly with the branches of other sciences in the forest of 

 knowledge. The systematist would, indeed, be at a loss to classify 

 our work, if in classification he thought to keep it apart from other 

 kinds of work. Better let it grow up naturally with interlacing tree- 

 tops and crowded underbrush, each tree showing its individualized 

 effort in the universal competition, than seek to trim it into an orchard 

 of separate trees. The departments and sections into which we are 

 divided in this congress do not represent objectively disconnected 

 groups and units of knowledge, but associated parts in contiguous 

 growths of acquisition ; we must not hesitate to go out of conventional 

 bounds and to trespass, as it is called, on other departments, when it 

 is to our advantage. Others are surely free to do the same by us. 

 When we employ methods called mathematical and physical in our 

 study of the winds, the profit is not only found in direct results, but 

 also in the use of deduction and experimentation, so familiar in 

 mathematics and physics, and so much less practiced, yet so much 

 needed in all parts of earth science; in return we supply data for the 

 study of the phenomena of gases on the largest terrestrial scale. 



We must be chemists, geometricians, and physicists in studying 

 the minerals of the earth's crust; and in return we supply to the 

 chemist a great variety of natural compounds, and to the physicist 

 the material basis for a remarkable variety of optical phenomena. 

 We must indeed marvel at the skill displayed by minerals — which 

 invade, colonize, migrate, and settle again in the dark inner world — 

 in handling external rays of light, and we may wonder if they have 

 not had some preliminary practice on radiations of a kind that physi- 

 cists have yet to describe. Admirable also are the crystalline forms 

 that give realization to the early inventions of geometers, much in 

 the way that planets and comets give us in their orbits great natural 

 examples of the conic sections, familiar for centuries as mathematical 

 abstractions. 



But it is particularly with biology in all its branches that we have 



