CALCAREOUS CONCRETIONS. OF KETTLE POINT 147 
bicarbonated water that may be in contact with it.’ Monocar- 
bonate is precipitated about the fragment and a double biproduct 
is formed of water less strongly charged with the bicarbonate 
than before, and of carbon dioxide, which may be kept in solu- 
tion in the water. The volume of new monocarbonate, together 
with that of the biproducts, is greater than that of the original 
bicarbonate ;* expansion is necessary. The result would be the 
development of pressure directed centrifugally with respect to 
the fragment. This pressure will be the sum of all those minor 
pressures produced by the single decompositions of bicarbonated 
water entering by each of a million passages to the point where 
the solid carbonate is reached. The integrated force may have 
great efficiency. It would tend to expel the water from the sur- 
rounding capillary passages. If the expulsion kept pace with the 
crystallization, the space between the mineral and the adjacent 
rock-substance would soon be completely closed and crystalliza- 
tion and growth of the concretion would cease. 
But the experiments of Jamin? have proved that equilibrium 
may exist between two unequal pressures affecting the ends of a 
capillary tube, provided a column of liquid occupying the tube 
be interrupted by bubbles of air. The presence of the latter 
excites capillary attraction which is so strong as to take up 
It is a familiar fact that crystallization can often be brought about, when not 
produced by other means, by introducing a crystal of the substance, the crystallizing 
of which is desired. Further, the mass of substance dissolved in water and coming 
in contact with a mineral, is very small compared with that of the mineral; if there 
ensue a chemical reaction, it is the large mass of the mineral that regulates the laws of 
affinity. Thus, solid carbonate of barium decomposes dissolved bicarbonate of 
calcium, and solid calcium carbonate decomposes dissolved barium carbonate ; 
4 fortiori, solid calcium carbonate will decompose dissolved calcium carbonate, i. e., 
the bicarbonate. Cf. BiscHor, Lehrbuch, Band I, p. 114. 
2 That expansion will result has unfortunately not yet been proved by experiment 
in the case of CaCOg, but it is inferred from the law that expansion of volume follows 
on the separation of salts from their solutions in those instances where increased pres- 
sure aids solubility. Engel has determined that the solubility of carbonate of lime 
in carbonated water increases very rapidly with an increase of pressure, e. g., 
doubling with a rise of pressure from one to six atmospheres. Comptes Rendus, Vol. 
Cl, p. 949. 
3Comptes Rendus, Tome L, 1860, pp. 172 and 311. 
