No less than twenty workmen are engaged in these operations, and during the whole time the apartment is kept perfectly still, lest a motion of any kind should set the air in motion, the slightest disturbance of the surface of the plate being calculated to impair its value. "The spectacle of such a vast body of melted glass," observes Mr. Parks, "poured at once from an immense crucible, on a metallic table of great magnitude, is truly grand; and the variety of colors which the plate exhibits immediately after the roller has passed over it, renders this an operation more splendid and interesting that can possibly be described."[15] [Footnote 15: Lard. Cyclo.] To attempt the briefest outline of the vast number of objects that are composed of glass, and the variety of processes to which the material is subjected in their production, would carry us far beyond the limits within which we are unavoidably confined. Even the most trifling articles of daily use, apparently very simple in their formation, involve many elaborate details. Take a watch, for example. The history from the furnace to the workshop, of those parts of a watch which are composed of glass, is full of curious particulars. The watch-glass maker exercises a function distinct from any one of those we have hitherto been considering. He receives from the blower an accurate hollow globe of glass, measuring eight inches in diameter, and weighing exactly twelve ounces, which is the guarantee at once of the regularity and thinness of the material. Upon the surface of this globe the watch-glass maker traces with a piece of heated wire, sometimes with a tobacco pipe, as many circles of the size he requires as the globe will yield, and wetting the lines while they are yet warm, they instantly crack, and the circles are at once separated. He finds the edges rough, but that is got rid of by trimming them with a pair of scissors. The circles thus obtained are deficient, however, in the necessary convexity; he accordingly reheats them, and, with an instrument in each hand, beats or moulds them into the precise form desired, much in the same manner as a dairy-maid, with her wooden spoons beats a pat of butter into shape. The edges are now ground off, and the watch-glass is complete. The preparation of the dial, which is composed of opaque white glass, ordinarily known as enamel, is a much more complicated work, involving several minute processes and a larger expenditure of time. Upon both sides of a thin plate of slightly convex copper, bored with holes for the key, and the hour and minute hands, is spread with a spatula a coat of pounded glass which has gone through several stages of solution and purification before it is ready for application. In the management of this operation, and the absorption of any moisture that may linger in the enamel, considerable care and delicacy of hand are necessary. As soon as the dial-plate is perfectly dried it is put into the furnace to be heated gradually.