THEORIES OF METALLIC VEINS. 551 
explain the manner in which these chasms in 
solid rocks have become filled with metallic 
ores, and with earthy minerals, often of a diffe- 
rent nature from the rocks containing them. 
Werner supposed that veins were supplied by 
matter descending into them from above, in a 
state of aqueous solution ; whilst Hutton, and his 
followers, imagined that their contents were in- 
jected from below, in a state of igneous fusion. 
A third hypothesis has been recently proposed, 
which refers the filling of veins to a process of 
Suhlimation from subjacent masses of intensely 
heated mineral matter, into apertures and fissures 
of the superincumbent Rocks.* A fourth hypo- 
thesis considers veins to have been slowly filled 
by Segregation, or infiltration ; sometimes into 
contemporaneous cracks and cavities, formed 
* In the London and Edin. Phil. Mag. March, 1829, p. 172, 
Mr. Patterson has pubHshed the result of his experiments in 
making artificial Lead Ore (Galena) in an Earthen tube, highly 
heated in the middle. After causing the steam of water to pass over 
a quantity of Galena, placed in the hottest portion of this tube, the 
water was decomposed, and all the Galena had been sublimed from 
the heated part, and deposited again in colder parts of the tube, in 
cubes which exactly resembled the original Ore. No pure Lead 
was formed. From this deposition of Galena, in a highly crys- 
talline form, from its vapour in contact with steam, he draws the 
important conclusion, that Galena might, in some instances, have 
been supplied to mineral veins by sublimation from below. 
Dr. Daubeny has found by a recent experiment that if steam 
be passed through heated Boracic Acid, it takes up and carries 
along with it a portion of the Acid, which per se does not sub- 
lime. This experiment illustrates the sublimation of Boracic Acid 
in volcanic craters. 
