126 
ANNALS NEW YORK ACADEMY OF SCIENCES 
That meteoric waters charged with such other substances as those above 
mentioned would have a much greater solvent action than pure water upon 
trap rock, while probable, seems not to have been as yet experimentally 
established. 
In either case meteoric water, penetrating the New Jersey trap from 
above, finds its way downward through numerous crevices and joints in the 
rock, even when they are only of microscopic width, dissolves the trap on 
both sides of, and thus gradually widens them. The more or less concen¬ 
trated solution collects in natural cavities or larger crevices previously formed 
and there, apparently, deposits chiefly in crystals the complex materials it 
carries. 1 
By what process is the solution caused to deposit its contents ? It seems 
little likely to be evaporation, but there are several other known processes 
which jointly or separately could possibly result in the production of these 
minerals from solution under the apparent conditions. For-example, the 
water could become charged with a soluble constituent of the trap, part or all 
of which it might have to deposit, as in its further progress it acquired 
another constituent. 2 This is a known process of deposition from solution 
but not of common occurrence. 
Another cause for the deposition of substances from solution is a change 
of solubility with change of temperature. Some substances are more 
soluble in warm, others in cold water. A change of one degree in temper¬ 
ature in a saturated solution could cause some deposition of its contents. 
Water, upon freezing, excludes all substances it may hold in solution, whether 
solid, liquid or gaseous. In case such a solution as that above described 
were frozen in a fissure in the rock, upon again becoming liquid it could 
drain av T ay without redissolving the material it had deposited. 
Variations of pressure, acting in most cases inversely to variations of 
temperature, increase or decrease the saturation capacity of solvents. 3 Thus 
the solvent action of meteoric v T ater may be increased the deeper a descend¬ 
ing column penetrates below the surface. Upon the subsidence of such a 
column to a subsurface level during a dry interval, or upon the escape of 
such v r ater as spring water with consequent release of pressure, this condi¬ 
tion is reversed and perhaps a deposition of dissolved material may occur. 
The principle of diffusion also may be involved in the sorting out of the 
dissolved substances and their deposition to form these minerals. 4 It seems 
1 According to Bischoff (Chem. & Phys. Geol. V. 2; London 1859 pp. 116 & 137) anal- 
cite and natrolite are the only zeolites which do not contain silicate of lime and the only ones 
that could have been produced from water containing C0 2 . 
2 W. A. Miller: Elem. Inorg. Chem., Part 1, Chem. Phys. p. 63, N. Y., 1864. 
3 J. P. Iddings: Igneous Rocks, Vol. I, p. 158, New York, 1909. 
4 Id., p. 70. 
