G. H. HALLIGAN. LXXV. 



Four men are employed on the ordinary boring apparatus 

 shown in Fig. 1. This illustration shows the sheer legs on two 

 punts coupled together as used in boring afloat, and the tools 

 here described are those employed on this work, though, with 

 rery little modification, they could be, and, in fact, are being 

 used for land boring. There are, however, certain essential 

 differences, and these will be noticed as we proceed. The punts 

 here shown are each 37 ft. long, 12£ ft. wide, and 3^ feet deep, 

 and are large enough to enable any boring to be sunk within the 

 capacity of the apparatus. They are temporarily bolted together, 

 having a space one foot wide between them. In this space the 

 boring tubes may be lowered as required, generally in the centre 

 of the opening so that any strain caused by lifting or forcing 

 down the tubes may be equally distributed and save injury to 

 the punts. 



Four inch tubes are generally used, having an inside diameter 

 of 3f in. This size has been found to be sufficiently light to 

 allow of convenient handling, and large enough to allow fairly 

 coarse gravel to be picked up with the tools, without the necessity 

 of too much pounding. With smaller sized tubes, the tools must 

 be so small that sufficient strength cannot be given them to allow 

 for wear and tear, while if larger tubes are used, the outfit 

 becomes too heavy and unwieldy for convenient and economic 

 working. 



The author would here like to say a word in favor of butt- 

 joints for all tubes where much forcing down or hammering has 

 to be done. Experience has not shown that the union joint 

 offers any more obstruction to the withdrawal of the tubes than 

 the swelled joints, but it is infinitely better as regards its ability 

 to withstand driving, and it is not so liable to become unscrewed. 

 Where it is necessary to purchase swell-jointed pipes, it is found 

 to be economical to have the female screw cut off and union 

 joints made before starting any deep boring. On several 

 occasions the tubes have telescoped at the swelled joints, when 

 subjected to severe driving through obdurate material such as 

 stiff clay, coarse gravel, or indurated sand. 



