302 
GEOLOGY: S. TABER 
area, their structure and orientation, pressure, temperature, and the 
composition of the solution. Hence, different faces may develop under 
different conditions of growth. 
Most of the phenomena hitherto cited in support of the hypothesis 
that there is a 'linear force of crystallization' are to be explained by the 
fact that the growing crystals have been in contact with a supersatu- 
rated solution in only one direction or that the concentration.of the solu- 
tion has been greater in one direction than in others. It is probable that 
the pressure effects observed during crystallization are due chiefly to the 
separation of solid matter from solution rather than to the growth of 
crystals, and, under favorable conditions, the pressure developed in this 
way may greatly exceed the crushing strength of the substance. 
Crystals grow in directions in which external forces oppose growth 
whenever the surfaces under pressure are in contact with a film of super- 
saturated solution, and it is possible to supply the material for growth 
by slow diffusion through subcapillary spaces, as great resistance is 
offered to the expulsion of solution from such openings. The conditions 
requisite for the growth of crystals under pressure commonly obtain in 
the rocks of the earth's crust, and many phenomena connected with the 
metamorphism of rocks, the growth of concretions, and the formation 
of mineral deposits are difficult of explanation under any other hypothe- 
sis than that growing crystals have made room for themselves by exerting 
pressure on the surrounding material. 
iLavalle, J., Paris, C.-R. Acad. Set., 36, 1853, (493). 
2Kopp, H., Ann. Chem. Pharm., Leipzig, 94, 1855, (124). 
3Lehmann, O., Molekularphysik, 1, (342), Leipzig, 1888. 
4 Becker, G. F., and Day, A. L., Proc. Washington Acad. Sci., 7, 1905, (285-287). 
5 Bruhns, W., and Mecklenburg, W., Jahresber. Niedersdchs. geol. Ver. Hanover, 6, 1913, 
(22-115). 
8 Becker, G. F., and Day, A. L., Chicago, J. Geol, Univ. Chic, 24, 1916, (315-325). 
. 7 Taber, S., New Haven, Amer. J. Sci., (Ser. 4), 41, 1916, (535). 
8 Becker, G. F. and Day, A. L., Chicago, J. Geol, Univ. Chic, 24, 1916, (325-329). 
Uhid., (313). 
10 Taber, Stephen, The origin of veins of the asbestiform minerals, these Proceedings, 2, 
1916, (662). 
" According to Traube ammonium nitrate goes into solution with expansion in volume; 
Zs. anorg. Chem., Hamburg, 3, 1892 (1). This reference cited in G. P. Baxter's Changes in 
volume upon solution in water of the salts of the alkalis, /. Amer. Chem. Soc, Easton, Pa., 
33, 1911, (923). 
12 For description of this experiment see The genesis of asbestos and asbestiform minerals 
by Stephen Taber, Bull Amer. Inst. Min. Eng. No. 119, p. 1987, Nov. 1916. ■ 
