incorporating machine is nothing more than a couple of runners or huge wheels, weighing four and a half tons each, which revolve one after another on their edges in a bed of metal supplied with a deep wooden rim, which gives it much the appearance of a huge kitchen candlestick. Into this dish the black powder is placed, together with a little water, which varies in quantity, from four pints in winter, when the atmosphere is charged with moisture, to ten in the summer, when the desiccating quality of the air is very great. For four hours this pasty mass is crushed, ground, and mixed by the action of the runners. The precautions taken against explosion teach the visitor the dangerous nature of the ground he is treading. Before he puts his feet across the threshold he must encase them in leathern boots huge enough to fit Polyphemus, and guiltless of iron in any form whatever; even his umbrella or stick is snatched from him, lest the ferrule should strike fire, or accidentally drop among any part of the machinery whilst at work. The machinery is even protected against itself. In order to avoid the possibility of the linch-pins which confine the cylinders to their axles falling down, and by the action of "skidding" the runner, producing so much friction as to cause an explosion, receptacles are formed to catch them in their fall. As small pieces of grit, the natural enemy of the powder-maker, might prove dangerous if mixed with any of the "charges," the axle sockets of nearly all the wheels are constructed to expand, so as to allow any hard foreign body to pass through just in the same manner in which the fine jaws of the larger serpents are loosely hinged, to enable them to get over at one gulp such a bulky morsel as a full-grown rabbit.