CALCAREOUS CONCRETIONS OF KETTEE POINT 149 
to that produced by the freezing of water in a closed vessel, 
being caused by a change of volume, and not by the thrust of 
the crystals as such. 
Much of this general scheme can be applied with certainty 
to the Kettle Point concretions. Bicarbonated water unques- 
tionably was the source of the calcite substance; the decompo- 
sition was induced locally at the call of pre-existent carbonate, 
and the double biproduct described must have resulted. Since 
the joints in the shale are undoubtedly due to desiccation, it is 
but fair to suppose that the concretions antedate them. The 
presence of hydrocarbons during the concretionary growth is 
likewise.reasonable. The resulting surface tension in this deep- 
lying water would thus bring about capillary action which was 
especially powerful on account of the extremely small size of 
the channels through which water could migrate in the shale. 
The shape of the growing concretions will depend primarily 
on the resistances offered to displacement by the shale, and, per- 
haps, secondarily, to the rate of supply of bicarbonate. From 
the homogeneous character of the shale, we are led to believe 
that both of these actions will be nearly equal in all directions 
throughout the rock, with, however, a slight advantage in power 
of resistance to be ascribed to the direction at right angles to 
the plane of stratification. The resulting form of the concre- 
tions would, in consequence, be that of a sphere or of a spheroid. 
The calcite crystals will assume radial positions according fora 
law of crystal growth that does not concern us here; they will 
grow outward into the shallow space offered by the outward 
thrust until the biproduct has slowly diffused through the argil- 
laceous wall. 
In conclusion, then, it may be stated that the concretions 
were formed in place within the shale, that they antedate the 
period of joint development and final consolidation of the sur- 
rounding rock, that the local deformation of the shale accompa- 
nied the process of crystallization, and that the energy of the 
deformation appears to have been derived from the change of 
volume induced by the breaking up of the bicarbonate into 
