NEW YORK ACADEMY OF SCIENCES 645 



enormous volume has, however, been brought home to us in 

 recent years, with great force, by the outbreak of Mont Pele\ and 

 we of this academy, thanks to the efforts of our fellow-member, 

 Dr. E. O. Hovey of the American Museum of Natural History, 

 have had them placed very vividly before us. It is on the whole 

 not surprising that to the meteoric waters most observers in 

 the past have turned for the chief, if not the only, agent. I 

 will, therefore, first present, as fully as the time admits and as 

 fairly as I may, this older view which still has perhaps the 

 larger number of adherents. 



Except in the arid districts rain falls more or less copiously 

 upon the surface of the earth. The largest portion of it runs 

 off in the rivers; the smallest portion evaporates while on the 

 surface, and the intermediate part sinks into the ground, urged 

 on by gravity, and joins the ground-waters. Where crevices 

 of considerable cross-section exist, they conduct the water 

 below in relatively large quantity. Shattered or porous rock 

 will do the same, and we know that open-textured sandstones 

 dipping down from their outcrops and flattening in depth lead 

 water to artesian reservoirs in vast quantity. As passages and 

 crevices grow smaller, the friction on the walls increases and 

 the water moves with greater and greater difficulty. When 

 the passage grows very small, movement practically ceases. 

 The flow of water through pipes is a very old matter of investi- 

 gation, and all engineers who deal with problems of water 

 supply for cities or with the circulation of water for any of its 

 countless applications in daily life must be familiar with its 

 laws. Friction is such an important factor that only by the 

 larger natural crevices can the meteoric waters move downward 

 in any important quantity or very appreciable velocity. They 

 do sink, of course, and come to comparative rest at greater or 

 less distance from the surface and yield the supplies of under- 

 ground water upon which we draw. 



The section of the rocks which stands between the surface 

 and the ground-water is the arena of active change and is that 

 part of the earth's crust in which the meteoric waters exercise 

 their greatest effect. Rocks within this zone are in constant 

 process of decay and disintegration. Oxidation, involving 



