186 Scientific Intelligence.—Miscellaneous. 
rities, to a strict sense of duty, in so far as their charge lies in re- 
gard to the protection of castles, fine old mansions, cathedrals, 
churches, and universities. We cannot refrain from adding, that 
the Terrace Building of our Own Unwersity is already falling into 
rapid decay. 
*« Silica,” says Mr Barlow, “ is one of the most abundant sub- 
stances known. Quartz, common sand, &c., flint, chalcedony, opal, 
&c., and a variety of sand described by Mr J. T. Way,* may re- 
spectively be taken as examples of crystallized and uncerystallized 
silica, Under all these forms silica is capable of combining with 
bases as an acid. Heat is, however, essentially necessary to effect 
this combination,—a combination of which all the well-known sili- 
cates, whether natural, as felspar, mica, clay, &c., or artificial, as 
glass, slags, &c., are the results. The common forms of insoluble 
glass are produced by the union of silica with more than one base. 
ut, when combined with an alkaline base only, silica forms a so- 
luble glass, the degree of solubility of which depends on the propor- 
tion which the silicic acid bears to this alkaline base .... . This 
soluble silicated alkali (or water-glass) may be prepared by various 
processes. If sand be used, 15 parts of fine sand, thoroughly incor- 
porated with 8 parts of carbonate of soda, or with 10 of carbonate 
of potash, and 1 of charcoal fused in a furnace, will produce a sili- 
cated alkali which is soluble in boiling water. Messrs Ransomes 
obtained this silicated alkali by dissolving broken flints in a solution 
of caustic alkali at a temperature of 300° Fahr. And more re- 
cently, Mr Way has observed that the sand which he has described 
will combine with caustic alkali, at boiling heat, also producing a 
water-glass. 
«‘ This water-glass has been applied to several important pur- 
poses, three of which were specially noticed. 
“1. To protect Building-stones from decay.—The stone sur- 
faces of buildings, by being exposed to the action of the atmosphere, 
become liable to disintegration from various causes. Moisture is 
absorbed into their pores. The tendency of their particles to sepa- 
rate, in consequence of expansion and contraction, produced by alter- 
nation of temperature, is thus increased. Sulphurous acid is always 
present in the atmosphere of coal-burning cities, and cannot but 
corrode the calcareous and magnesian ingredients of oolites and dolo- 
mites. It is true that good stone resists these sources of injury for 
an indefinite time, but such a material is rarely obtained. As a 
preventive of destruction, whether arising from physical or chemical 
causes, it has been proposed to saturate the surfaces of the stones 
with a solution of the water-glass. 
‘* Tt is well known that the affinity of silica for alkali is so feeble 
* Quarterly Journal of Chemical Society, July 1, 1853, and Journal of 
Royal Agricultural Society, vol. xiv., part 1. 
