go REVIEWS 
relatively large and that in the lower very small. An estimate of this 
kind gives an impression large or small according to the point of view. 
Regarded by itself, it is large, but compared with the whole hydro- 
sphere it is but a small factor and does not very appreciably add to the 
oceanic volume. It probably does not amount to so much as the prob- 
able error in the estimation of the volume of the ocean and other 
superficial waters. If the water of hydration be added to it, the state- 
ment may not improbably still hold true. 
In the treatment of the general movements of the ground water 
three categories are recognized: (1) Gravitative, (2) thermal, and (3) 
capillary movements. The oscillations in the flow of springs and arte- 
sian wells are illustrated by autographic records and their relations to 
barometric changes demonstrated. Even the sudden barometric 
changes accompanying a shower are sometimes sharply. recorded. 
Diurnal changes in temperature are shown to effect thé rate of seepage. 
This is attributed chiefly to the indirect effect of the temperature 
through the expansion of the gases in the soil. Movements of ground 
water are ascribed to rock consolidation and crust deformation. Of 
the 25 to 50 per cent., by volume, of water inclosed in the sediments, 
when first laid down, a considerable part is forced out as the sediments 
settle into greater compactness, and finally pass into indurated rock. 
By an ingenious device on automatic flow from the base to the top of 
a cylinder of settling sediments was secured against a head of six inches. 
In the dynamic consolidation of rocks, a still larger per cent. of the 
inclosed water is forced out. The growth of grains and the filling of 
pore-spaces is a concurrent source of expulsion of water. Limestones 
as now taken from the quarries have, as a rule, a pore-space varying 
from less than 1 per cent. to 7 or 8 per cent. at most; so that the 
final formation of every 1000 feet of compact limestone means an ex- 
pulsion of water from these beds during the process of growth and con- 
solidation amounting to not less than one fourth, and possibly as 
much as one half, of the present volume of the rock. 
For the capillary movements of ground water recourse must be had 
to the paper itself, as the tables cannot be briefly and adequately sum- 
marized. 
The configuration of the ground water surface is illustrated by 
contour maps and the flow dependent on this configuration diagram- 
matically indicated. The changes in the configuration that result from 
precipitation are shown by tables and by diagrayns. 
