30 Dr. Playfuir’s Lecture on the Great Exhibition of 1851. 
shave it with a knife. This process was tedious and imperfect, 
and the following simple one is now used. Lime-water dissolves 
the bulbous root of the hair, when the hides are immersed in it 
for some time, and the hair may then be readily removed by a 
blunt instrameut. By this simple process one man can remove 
the hair from a hundred kid-skins in about an hour. Still the 
immersion requires several weeks, while the addition of red orpi- 
ment to the lime, as practised by the sheep-skin manufacturérs of | 
France, reduces the time to a few hours. 
formed, by Mr. Bevington, that the sum annually paid to the 
collectors and workmen employed in using this apparently 
worthless substance, is not less than 5000J. in the metropolis — 
The currier shaves leather to render it of equal thickness, and — 
the shavings are treated as waste, scarcely fit for the manure- 
heap, but chemistry has shown that they contain much nitrogen, 
which renders them well adapted for the formation of the beauti- 
ful color known as Prussian blue. 
Mineral and Metallic Manufactures.—The mineral and me- 
tallic manufactures are those which obviously have derived most 
advantages from chemistry. Glass and pottery are in fact chem- 
ical manufactures. The hard-won experience of two thousand 
years in China has been given to Europeans by a few years’ ap- 
plication of chemistry. Glass, made by the ancients from the 
ashes of ferns and other plants, is now formed by soda artificially 
produced from sea salt. - The Exhibition showed that this man- 
ufacture, far advanced as it is, may still be susceptible of improve- 
ment ; for, in the French department, glass was shown in which 
zinc and barytes were substituted for lead. The hardening and 
production of steel, the discovery of many new alloys endowed 
with properties most important to the arts, and the electrotyping 
of metals, are familiar examples of chemical appliances; but this 
very familiarity renders it unnecessary that I should dwell upon 
them. I, therefore, from want of time, leave these important 
chemistry may 
be less. palpable to the general er, 
e 
ures, and pass on to others, in which the influence of — 
