TRANSACTIONS OF THE SECTIONS. 125 
On the Solvent Power exercised by Water at high temperatures on 
Siliceous Minerals. By Juiius JErFREYs. 
“The few remarks I have to offer have reference to a paper read 
before the Royal Society of London last spring. It briefly related an 
experiment made to determine the action of water, in the form of its 
vapour, upon siliceous minerals at very intense heat. The experiment 
was upon a large scale, and consequently very costly, and the re- 
sults were curious, as establishing-a very powerful action by water 
on siliceous minerals, when the temperature is sufficiently high.” Mr. 
Jeffreys exhibited an enlarged drawing to the Section, showing the 
construction of a large boiler, erected near Furrukabad, a large city 
800 miles north-west of Calcutta. It was the only one of the kind in 
India, and was employed for vitrifying brown stone ware, the manu- 
facture of which Mr. Jeffreys had succeeded in introducing into 
that country. It was heated by four exterior furnaces, each six feet 
long and five wide. The kiln inside was fifteen feet in diameter and 
twenty-four feet high. The fuel was wood, and the utmost effect any 
alkali which might be supposed to rise in its vapour ordinarily pro- 
duced, was a slight glazing of some of the brick surfaces in the kiln, 
near the entrance of the flame; an appearance which is also seen 
with other fuel, and with which all manufacturers are familiar. <“‘ For 
the sake of experiment, I pulled down the four furnaces and rebuilt 
them, after having made between each and the kiln a deep pit as wide 
as each furnace, and only nine inches from front to back. About 
three feet of water was put into each pit, and was renewable from 
without. Some felspathic and siliceous minerals were placed in the 
way of the current, just inside of the kiln, and upon some of the arches 
a few articles of ware were placed, that any action upon them might 
be observed. Below a full red heat little effect was perceived, but at 
a heat above that of fused cast iron a rapid solution of mineral matter 
took place. This heat was continued ten hours. When the kiln was 
opened, more than a hundred weight of mineral matter, though in a 
very dense and refractory form, had been dissolved, and carried awa 
in the vapour. The wall was eaten away, as shown by the dotted line, 
and presented a rough, and quite unglazed surface, like loaf-sugar 
partially melted by water, or as if eroded by some animal; and nothing 
of the smooth glazed surface, which invariably attends the action of 
alkali on a siliceous surface. Some articles of ware in the hottest 
situations were partially eaten through; but on the uppermost arch, 
where the heat was only a full red, a curious phenomenon appeared. 
The articles there had received, exterior to their own brown gloss, and 
loosely encrusting it, a complete frosted coat of silica, having the ap- 
pearance of a candied surface. It was manifestly a precipitation from 
the mineral vapour, and in fact a hoar frost of silica. There was pro- 
bably from half an ounce to an ounce on each vessel, and several 
pounds altogether were thus precipitated; but by far the greater part 
of the mineral vapourized was, as might be supposed, carried away in 
the current. Since this powerful action was apparently entirely due 
