148 VAR CIIMAIEIO) él, JOVAIL VG 
several atmospheres of pressure applied at one end of the tube. 
The force so expended is represented in the compression of the 
air bubbles and in changing the form of the air menisci; surface 
tension is thus overcome. The movement of the bubbles pro- 
gressively decreases in the direction of the greater pressure until 
one is reached which is not disturbed at all so long as the pres- 
sures remain constant. The bubbles act lke so many buffers. 
Any capillary tube filled with water interrupted by any insoluble 
gas or liquid possessing a lower surface tension than water, will 
exhibit the same phenomenon. Let us return to our incipient 
concretion. 
Round about the grain of carbonate, there is an infinite net- 
work of capillary passages largely occupied by water in the 
early history of the rock. Along with the water, are gaseous 
and liquid hydrocarbons that are slowly being evolved by the 
decomposition of organic matter. The distribution of the hydro- 
carbons will be such as to bring about capillary attraction, and 
therewith the possibility of differential pressures within the 
water-mass, though it be in equilibrium throughout. Thus at 
the capillary film separating lime fragment and argillaceous wall, 
we may have great outward pressure unaccompanied by the 
expulsion of water along the channels leading from the country 
rock to the fragment. The latter is girt about with a mesh of 
capillary passages enormously resistant to movement of the con- 
tained liquids, and permitting of greater hydrostatic pressure 
within than without. The form of the mesh itself may change 
however, without interfering with its function as a buffer. The 
centrifugal pressure will then be occupied in deforming the rock, 
and it may conceivably be aided by the expansive energy of the 
freed CO,. Fresh supplies of bicarbonated water will slowly 
diffuse into the capillary space between concretion and rock and 
further the displacing process. The solid carbonate as it were, 
keeps pulling a trigger that sets off the reaction of decomposi- 
tion, which does not occur at a distance from the fragment. 
The biproduct cannot escape as fast as formed and the country- 
rock must be crowded away. The deformation is then, analogous 
