Britain at Work
A Pictorial Description of Our National Industries

6o BRITAIN This huge blade is suspended above the stone with its edge parallel to it, and being swung with a pendulum-like motion by powerful machinery, the saw slowly but surely cuts its way into the granite. Unlike an ordinary saw, however, the granite saw has no teeth, and having an edge a quarter of an inch thick, the question will at once arise, how can a blunt instrument of this description cut through several feet of one of the hardest stones in existence? Well, the saw might swing to arid fro for years, with no appreciable effect, if it were not for the application of an abrasive in the shape of grit or grains of chilled metal, exactly like bird-shot, upon which the edge of the saw works. Water being, of course, applied to prevent heating, a mixture of shot and powdered stone is formed, consti- tuting a kind of sludge which is constantly ladled into the saw-cut by the man in attendance. The process of slicing up a large block of granite is necessarily a gradual one, a depth of 2 J/ inches per hour being considered good work. This means that to saw through a block five feet in depth would take twenty-four hours, or nearly three working days. Nevertheless, the use of the granite saw saves an immense amount of manual labour, and if the opera- tion is carefully carried out, the sawn surface scarcely requires to be touched by the dressing hammer, and is ready for the carving shed or the polishing mill. When placed on the polishing carriage, as the machine is called, the granite passes through three distinct stages before acquiring the beautiful gloss so much admired. The first medium used is the shot already referred to, but of a finer grain than that used for sawing. The shot is rubbed over the surface of the stone with revolving metal rings, until smoothness is obtained. Emery powder is then applied, which pro- duces a dull polish. Last of all putty powder is rubbed on with felt attached to the revolving rings, and the polishing process is complete. A bed of granite 23 feet in length will be polished in two days To polish mouldings, iron plates are made to fit the curves of the stone, and the process is carried out with the mediums described, but applied to the mouldings by a machine AT WORK. called a pendulum, the action of which is explained by its name. Columns and urns are made to revolve on lathes, and the gritty substances being applied with the irons and felt, they, as it were, polish them- selves. When it is necessary to polish work carved in relief, as is almost invariably the case with orders received from French architects, men known as hand-rubbers are employed. The hand-rubbing process is, of course, much slower than polishing by machinery, but the same methods are used. The carving of Aberdeen granite was revolutionised a few years ago by the intro- duction of the pneumatic tool. The pneu- matic tool had been in use for a considerable time in England for caulking purposes, but the people of the United States were the first to apply it to granite, the pioneers of this idea being, it is asserted, Scottish- Americans. Broadly speaking, a pneumatic tool is a small cylinder within which a piston is driven by compressed air. The motion of the piston being communicated to an ordinary carving chisel, that tool when in use comes in contact with the stone at the rate of from 1,500 to 2,000 strokes per minute, very many more times, it will be admitted, than a workman could accomplish with an ordinary hammer. The air is generated by a steam compressor, and conveyed by metal pipes to the carving sheds. These pipes are tapped at intervals, and the air carried by indiarubber tubes to the tools held in the hands of the workmen. When directed by a skilful handicraftsman the pneumatic tool will accomplish work of the most minute and elaborate description. When applied to the stone it rapidly “ eats ” away the superfluous material, and flowers, fruit, heraldic shields, regimental crests, and designs of a like nature, are quickly repro- duced on the hard granite, with as much fidelity of detail as could be accomplished in Sicilian marble. For statuary the pneu- matic chisel is equally useful, and it is also extensively applied in the cutting of inscriptions. There are pneumatic surfacing machines for dressing large stones, but only a few are as yet in use in Aberdeen. The axe and the bush-hammer are the tools most extensively in use for fine dressing. When the dressing of a stone is done