Origin of Pegmatite. — Crosbij and Fuller. 167 
it is distinctly along this line, from Charpentier's view as a 
starting point, that we have advanced to the conception of a 
more perfect cooperation of heat and water. Referring to 
Williams' summary* of pegmatite theories, we learn that Elie 
de Beaumont in his famous essay "Sur les emanations volca- 
niques et metalliferes,"j- while accepting in the main the igne- 
ous and intrusive origin of pegmatites, introduced an impor- 
tant addition in assuming water and other mineralizing agents 
as necessary factors in their formation. Scheerer,+ in a con- 
temporary paper, attributed a still more important role to wat- 
er in the formation of pegmatites, holding what Hunt§ has 
designated as the theory of "granitic juice," a liighly heated 
aqueous solution of mineral substances impregnating the con- 
gealing mass and oozing out under pressure into the surround- 
ing rocks. Lehmann,|| in his large and excellent work upon 
"The Granulite District of Saxony," as quoted by Brogger, 
endeavors to account for the pegmatite veins of that region. 
He assumes the aqueo-igneous (hydatopyrogene) formation of 
granite, and pronounces the veins in a sense to be injection 
veins. "The granitic veins of the granulite district have or- 
iginated, no doubt, with the aid of more or less water, but 
this has not been atmospheric water which has percolated 
downward through the cracks of the granite, but it is erupt- 
ive water, which was given up from the granite to the sur- 
rounding rocks, and which, under peculiar conditions obtain- 
ing at great depths, was supersaturated with mineral matter." 
Lehmann assumes for the granitic magma a gelatinous consis- 
tency, which was to be accounted for, presumably, b}'^ the pre- 
sence of "'viscous silicic acid." "These fluid secretions of gran- 
ite may be compared to liot jelly." * * * * "The capacity of 
silica to form jellies with much or little water invites strongly 
to this hypothesis." "Between such a gelatinous magma and 
a saturated aqueous solution a large number of consecutive 
intermediate stages can be imagined. In this way, it seems 
to me, the connection between the pegmatitic veins and the 
ordinary granites, the remarkable segregations in the shape 
*U. S. Geol. Survey, Annual Report, 15, 67G. 
tHull. Soc. Geol. Fr. (II), 4, 12 (1847). ' 
tBull. Soc. Geol. Fr. (II): 4, 4(58. 
§Chem. and Geol. Essays, 189(1775). 
IjGranulitgebirge, 52-58. 
