492 SCIENCES OF THE EARTH 



The inferential element of our progress has worked most bene- 

 ficently. It is largely through our inferences that we have come to 

 recognize the interdependence of the different parts of earth-science. 

 The climatologist may remain as provincial as he wishes; or he may 

 enter through the gateway of present conditions the vast domains 

 of past time, and on the way make friends with all the world; for 

 he w T ill then join hands with the petrographer who has evidence of 

 ancient desert conditions in the form of the grains in certain sand- 

 stones; and with the paleontologist who infers the existence of 

 ancient ocean-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 

 treetops and crowded underbrush, each tree showing its individual- 

 ized 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 depart- 

 ments, 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 crusts; 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 

 physicists 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 nat- 



