[ 144 ] 



damaged, their function beincj nut to bore, but to prevent the 

 setting of those which perform the cutting from being worn down 

 by friction. The diamonds, weighing about two carats each, are of 

 the value of 24s per carat ; consequently, a " crown " is worth about 

 £40 ; and the diamonds will bore to a depth of 500 feet before re- 

 quiring to be re-set. They are set at a slight angle, and, as they 

 rotate, those on the outer rim cut the hole, whilst those on the 

 inner rim form the core ; the strata through which they pass 

 rising in a column inside the auger. The top of the auger has 

 a diminishing socket; that is, it is dome-shaped, into the apex 

 of which are screwed the boring-rods. These are in lengths 

 of 3 feet each ; and, as the auger descends, so the boring rod is in- 

 creased in length, by an additional piece being screwed on. 

 No mechanical pressui-e is upon the auger, the engine being 

 required to merely give it the rotary motion, leaving the 

 weight of the auger and rods to exercise the pressure necessary 

 for boring. And this is very slight — about 301bs. only, — but, as the 

 auger and rods naturally increase in weight as the former goes 

 deeper, and the latter are added to in number, — at the time of the 

 visit the weight was between three and four tons, — the 301b. pres- 

 sure is obtained by counter weights, a balance-beam supporting the 

 rods at one end, and taking the weights at the other. The crown 

 of the auger is kept cool by water being pumped to it, the water 

 returning to the surface after performing the double duty of cool- 

 ing the crown and rinsing away the debris ; its return being effected 

 by being forced up the inside of the rods by the core rising in the 

 auger. The flow of water is also an indicator of when the auger 

 ceases to bore ; that is, when it is fully charged with whatever 

 strata it is boring through. The core of earth rises in the auger 

 till it reaches the diminishing socket, when it effectually stops the 

 water rising through the rods, and leaves the crown rotating on the 

 bottom without cutting, inasmuch as it cannot proceed further in 

 its downward direction, in consequence of the diminishing socket 

 resting iipon the top of the core. Then comes the process of 

 drawing the core, and this is a very tedious operation. By revers- 

 ing the motion of the engine, the boring rods rise instead of 

 descending, and are unscrewed length by length till the auger 

 at last makes its appearance. This labour, at the depth of 

 the boring on the occasion of the visit, occupied about one hour 

 and a half ; the same time being consumed in lowering the auger 



