ater constantly plays upon the
plates, which are also constantly powdered with fine sand. The ashlars
turn on their axes thirty or forty times a minute, and the plates of
glass are usually smoothed and 'evened' on both faces now by these
machines in from eight to nine hours, including the time spent in taking
them out of the plaster after one face has been smoothed, and fixing
them anew in the plaster, that the other face may fare as well. Here
again a considerable economy of time has been made. And, after all, when
one looks into the practical production of any of these great marvels of
human industry, it is in this economy of time that the real advance of
modern science beyond the results of ancient invention seems to consist.
With all our nineteenth-century chorus of 'self-praising,
self-admiring,' where should we be if certain--for the most part,
uncertain and forgotten--men of genius had not invented the primordial
processes which made art and civilisation possible? The workshop came
first, and was the real marvel in the case of every great industry. To
talk of the 'invention' of the steam-engine, for example, is an
absurdity. The 'invention' was the engine, an invention as old as Egypt
or China. The discovery that steam could be made to work the engine is
the more modest modern achievement. In this industry of glass-making the
amazing thing is that it should have come into the mind of a man so to
apply the heat of burning wood to sands and silicates enclosed in an
earthen vessel as to convert them into an entirely new substance
possessing qualities not perceivable by any human sense in the sands,
the silicates, or the earth.

What our modern progress in chemistry and in mechanics has enabled the
makers of glass to do, is greatly to reduce the trouble and cost of
producing this entirely new substance, greatly to improve the quality of
the substance produced, and to extend the range of the uses to which it
can be applied.

What would the Egyptians, who paid their tribute in glass to Rome, have
thought of a serious order to pave the Via Sacra with blocks of purple
glass? Yet such an order could be executed now at St.-Gobain, and when
one sees the great flags weighing nine kilogrammes made here and used to
let light into the cellarage below the carriage-ways, for example, of
the huge Hotel Continental, at Paris, it comes easily within the
probabilities that the whole underworld of our great cities in time may
thus c