UNACCOUNTED-FOR GAS. 123 



secure an accurately round hole, and that practically the 

 whole of the cuttings fall into the main. A proper set of 

 drilling tackle, with a hollow drill that cuts out a disc of 

 metal, and tap on the same tool that cuts the screw 

 without loss of gas, is a good investment, even if there are 

 only a few services to put down in a year; and in the case 

 of a very small works, arrangements can be made to borrow 

 from a neighbouring works. 



Prevention is better than cure, and it is not a difficult 

 matter to test for soundness a length of main or service 

 when laid, and before it is covered in. Various kinds of 

 apparatus for this purpose are on the market. I have done 

 some good work with a small gasholder containing one 

 cubic foot, which can be filled with gas or air, and loaded 

 to any desired pressure, say 5o-tenths or 6o-tenths. The 

 pipe to be tested, having been carefully blocked at each 

 end, and services disconnected, or the main taps shut off- 

 disconnecting is the safest plan, or unscrewing the meter 

 inlet and putting a cap on the outlet of main cock, because 

 I have known a good deal of trouble to arise by a main 

 tap passing a foot or so per hour when nominally shut off 

 the holder is connected to it, and if there is any leakage, 

 the extent of it can be determined by timing the descent 

 of the holder. Another test is to put a pressure gauge on, 

 and to charge the pipe up to the required pressure with 

 gas or air. If the latter is used, a small bellows or foot 

 blower is preferable to blowing up with the breath. I have 

 a strong prejudice against blowing from the lungs into gas 

 pipes, under any circumstances. If the pipe is sound, the 

 pressure or the holder (whichever is used) will not fall. 

 The apparatus can also be applied to the testing of con- 

 sumers' supply pipes and fittings. 



With the continuous demand for gas at all hours of the 



