BOEING 



435 



of a pole or lover at the surface ; one end being firmly fixed in the ground between two 

 posts, the other being allowed to pass over the hole. From the end of this pole the 

 bore-rods are attached by means of a chain ; thus every time the borers strike the 

 chisel, the lever enables them to lift the rods high enough to give the necessary impetus 

 to the rods for the next blow. The chisel is occasionally withdrawn, and a long 

 bucket with a hinged valve at the bottom opening upwards, is attached to the rods, 

 and lowered into the hole. The borers press this down upon the material broken up 

 by the chisel, so that a quantity of debris becomes enclosed in the bucket, and is 

 drawn up to the surface. This process is repeated until the hole is made clear, and 

 ready again for the chisel. 



The rods are drawn by means of a windlass attached to the three legs, and are un- 

 screwed at every second joint, until the whole of them are drawn out. They have 

 to be again screwed together when they have to be lowered. 



175 



This style of boring is limited to a small depth ; the weight of boring rods becomes 

 so great with an increasing depth, that the borers, even when assisted by a lever, are 

 unable to lift them. A depth of about 300 feet may be safely bored in this way. 



The nature of strata bored through is ascertained from the material brought up by 

 the bucket ; and the borers having constantly hold of the cross-bar, any change of 

 strata is at once indicated by the stroke of the chisel against the various beds met 

 with, being imparted to the hands of the men, who acquire by experience great deli- 

 cacy of touch. A new description of spring has lately been used with the hand- 

 boring machine. This consists of several layers of india-rubber, about 1 inch square, 

 and 2 feet 6 inches long, increasing the number of layers as the weight of rods be- 

 comes greater. Each end of the india-rubber is fixed in strong iron clamps, one 



FF'2 



