Book IV. INSTRUMENTS OF SCIENCE. 377 



less than 10, a must be prefixed, so that Ic shall always show two figures ; for instance, I being at 46 

 auvi k at 4, the sum is 4604. The easiest way to guard against error is to read 46 and add the word hun- 



dred ; thus, forty-six hundred and four, and not four thousand six hundred and four. It is hardly 

 necessary to point out the advantage of having such an instrument. No country gentleman, who takes 

 the smallest ch.irge of his own affairs, should be without one ; as, by merely walking from one end to 

 tlie otlier of any road, hedge, wall, ditch, &c. with the odometer (which is not more troublesome than 

 a walking stick), he can tell the length of it much more correctly than by a measuring chain, which, to 

 say the least of it, requires two honest men, one at each end, and who must be both paid for their trouble ; 

 whereas the gentleman himself, whose honesty cannot be doubted, as he is not likely to cheat himself, 

 can, at no expense, measure with this instrument at least four times as quickly as those with the 

 chain, who have it also in their power to mismeasure, if I may use the expression, six inches every 

 time a peg is put into the ground ; but its principal uses are to check measurements already made, and 

 to measure off the size of any proposed improvements, such as plantations, gardens, &c. ( Trans. H. Soc, 

 vol. vi. p. 603.) 



2507. Good's improved instruments for boring the earth for water, draining, and other 

 purposes, may now be considered as having superseded all others, and we shall shortly 

 describe them. 



2508. The auger {fig. 238. a) is to be connected by the screw-head to the length of rods by which 

 the boring is carried on. This auger is for boring in soft clay or sand ; it is 

 cylindrical, and has a slit or opening from end to end, and a bit or cutting- 

 piece at bottom. When the earth is loose, or wet, an auger of the same form 

 is to be employed, but with the slit or opening reduced in width, or even 

 without a slit or opening. A similar auger is used for cutting through chalk, 

 but the point or bit at bottom should then project lower, and for that pur. 

 pose some of these cylindrical augers are made with moveable bits, to be 

 attached by screws, which is extremely desirable in grinding them to cutting 

 edges. 



2509. The hollow conical atiger (6), for boring loose sandy soils, has a spiral 

 cutting edge coiled round it, which, as it turns, causes the loose soil to ascend 

 up the inclined plane and deposit itself in the hollow within. 



2510. The hollow cylinder or tube (c), with a foot valve, and a bucket to be 

 raised by a rod or cord attached at top, is a pumping tool for the purpose of 



getting up waterandsand that 



would not rise by the auger. 



When this cylinder is lowered 



to the bottom of the bore, the 



bucket is lifted up by the rod 



and cord, and descends again 



by its own gravity, having a 



valve in the bucket, opening 



upwards like other lift pumps, 



whicJi at every stroke raises 



a quantity of water and sand 



iri the cylinder equal to the stroke, the ascent and descent 



of the bucket being limited by a guide-piece at the top of 



the cyhnder, and two small nobs upon the rod, which stop 



agamst the cross-guide. 



2511. The tool for gelling up broken rods (d) consists of a 

 rod with a small cylindrical piece at bottom, which the broken 

 rod slips through when it is lowered, and a small catch with 

 a knife-edge, acted upon by a back-spring. In rising, the 

 tool takes hold of the broken rod, and thereby enables the 

 workmen at top to draw it up. 



2512. Another tool for the same purpose {fig. 239. e) is 

 like a pair of tongs ; it is intended to be slidden down 

 the bore, in order that the broken rod may pass between 

 the two catches, which, pressed by back springs, will, when 

 drawn up, take fast hold of the broken rod. 



2513. The tool for widening the hole (/) is to be connected, 

 like all the others, to the end of the length of rods passed 

 down the bore ; this tool has two cutting pieces extending 

 on the sides at bottom, by which, as the tool is turned 

 round in the bore, the earth is pulled away. 



2514. The chisel or punch-pipe {g) has a projecting piece to be used for penetrating through stone. This 

 chisel is by rising and falling made to peck the stone and pulverise it, the small middle part breaking it 

 away first, and afterwards the bioad part coming into action. Another chisel, or punching-tool {h), is twisted 

 on itscutting edge, and is used for breaking away a greater portion of the stone. 



2515. A lifting tool (?) is used when it happens that an auger breaks in the hole. On one side of this 

 tool a curved piece is attached, for the purpose of a guide to conduct it past the cylindrical auger ; 



