MINING 



319 



Fig. 1487 is an iron bucket, or, as it is called in Cornwall, a kibble, in which the ope 

 is raised in the shafts, by machines called whims or whimseys, sometimes worked by 

 horses, and frequently by steam-power. The best kibbles are made of sheet iron, and 

 hold each about three hundred weight of ore: 120 kibbles are supposed to clear a 

 cubic fathom of rock. In place of the kibble, skips running in guides fixed on the 

 sides of the shafts are now used in the large and well-conducted mines. 



Fig. 1488 represents the wheel-barrow used underground for conveying ore and waste 

 to the foot of the shafts. It is made of light deal, except the wheel, which has a 

 narrow rim of iron. 



In all mines, to a greater or 1489 



a less extent, there will be 

 found accumulations of water; 

 it is necessary, therefore, to 

 adopt measures to ensure its 

 removal. The mineral trea- 

 sures, being brought to the 

 surface, necessarily undergo 

 a process of ' dressing,' that 

 is, the separation of the richer 

 from the poorer portion. For 

 a full account of dressing ma- 

 chinery, &c., see DRESSING 

 OF OEES. 



It sometimes happens that 

 the necessities of mining de- 

 mand the construction of 

 shafts in places covered with 

 water. Some years since a 

 very extraordinary case of this 

 kind was carried out at the 

 Wherry Mine, near Penzance, 

 where a cylinder of wood, 

 rising through the sea, formed 

 the entrance to a shaft sunk 

 into the mine. In a storm a 

 ship ran against this wooden 

 structure and destroyed it. 



M. Triger, engineer in the 

 department of Maine and Loire, 

 had the idea of making a well 

 in the very bed of the Loire 

 by means of compressed air. 

 A cylinder of thin iron, fig. 

 1489, serving as a cutting 

 machine, was sunk into the 

 alluvium; it was separated 

 into three compartments by 

 horizontal partitions. The upper compartment remained always open, the lower 

 compartment was the workshop, and between them was the middle one, which served 

 as the chamber of equilibrium, designed to be put in communication with either 

 the compartment above or the one below. The things being so disposed, they forced 

 into the bottom compartment, air compressed by a vapour-machine without inter- 

 mission. This air drove the water up a tube, of which the lower part was buried 

 in the bottom of the excavation, and of which the upper part was raised above 

 the cylinder. The workmen were then able to penetrate the first apartment and 

 open the second, which was afterwards hermetically closed, and in which the air of 

 ordinary pressure was put in communication with the compressed air in the third. 

 Having arrived in the third compartment, they excavated the sands, and caused the 

 machine to descend. As they accumulated, the sands excavated in the middle com- 

 partment, they had only to remove them by shutting the communication with the 

 bottom and opening that of the top. A pressure sufficient to balance the exterior 

 waters was maintained during the work, without sensibly incommoding the work- 

 men. 



It is evident that wells dug in the water-saturated earths must immediately be cased, 

 that is to say, covered with a casing of wood, of masonry, or of iron, solid and imper- 

 meable, which is able to resist the infiltration and pressure of the waters at the same 

 time. 



