Archive image from page 565 of Discovery Discovery discovery0304londuoft Year: 216 DISCOVERY because it is more costly, and tliat the cheaper method for winning the clay, shown in Fig. 3, is now coming Fig. 3.—showing .iiXOTHHR JIETHOD UMl' >vi;ii, GETTING THE BY MECH.\NIC.\I. into general use. By this method fossils are broken up and the vertical face cannot be inspected so easily. The clay is dug by mechanical diggers and is loaded into tip-wagons, which are drawn up a steep incline, such as is shown in Fig. 2, to the grinding-mills, which are somewhat simila
Archive image from page 565 of Discovery Discovery discovery0304londuoft Year: 216 DISCOVERY because it is more costly, and tliat the cheaper method for winning the clay, shown in Fig. 3, is now coming Fig. 3.—showing .iiXOTHHR JIETHOD UMl' >vi;ii, GETTING THE BY MECH.\NIC.\I. into general use. By this method fossils are broken up and the vertical face cannot be inspected so easily. The clay is dug by mechanical diggers and is loaded into tip-wagons, which are drawn up a steep incline, such as is shown in Fig. 2, to the grinding-mills, which are somewhat similar to mortar-mills. It is un- necessary to add any mateiial such as lime or sand, and usually it is unnecessary to add water, the clay itself being sufficiently moist, though not too moist ; most important of all, the clay may be used as soon as it is dug, and need not be stacked in the open for some weeks or months to mature, as is the case with some clays. After being ground and passed through sieves, the clay is sent to the pressing machines and, with a die, is pressed into bricks measuring 9 x 4I X 3 inches. These are removed by barrows and stacked in the large modern Hoffmann continuous kilns (shown in Fig. 2)—very familiar objects in some districts. In these kilns the bricks remain for some three weeks, their size being reduced by burning to 8f x 4i X 2| inches. The kiln is divided into some sixteen compartments in one of which the green, undried bricks are stacked. Flues and dampers communicate with each compart- ment, and from each compartment with the chimney. Feed-holes in the roof of each compartment are also provided By these devices the hot gases are drawn forward from a compartment in which bricks have been burnt, and introduced into a forward compart- ment for drying the green bricks. When these are dry, further heat can be introduced, and increased by the use of fresh fuel for burning them. For this pur- pose a high temperature is required. When the bricks ha
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