This is a very pretty process, and used to be performed by machines which bore the very pretty names of _valseuses_. That paviour's rammers should be called _demoiselles_ has always seemed to me an outrage and an impertinence, though I may suppose it finds its excuse in the short-waisted costumes of our grandmothers. But the movement of the glass-smoothing _valseuses_ was really a sort of waltz movement. The plates of glass were fixed with plaster on a solid rectangular table. Granite-dust was scattered upon the plates, and then a wooden plateau, armed on the under side with bands of cast iron or steel, was set to waltzing over it backwards and forwards with a semi-rotatory motion, the granite-dust supplied becoming finer and finer as the waltzing went on. Instead of these _valseuses_ two great plates of glass are now fixed side by side with plaster on huge tables, and two large ashlars are set turning by steam on their own axes while they describe a great orbit over the plates of glass. A stream of water 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.