LAYING OUT THE DESIGN OF WORKS. 49 



done, the tower scrubber is not worked to the full advantage 

 A non-mechanical washer, which depends on the action of 

 pressure to force the gas through the liquid, and increases 

 the back pressure to the extent of 3 inches or more, is out 

 of the question. A mechanical washer actuated by a small 

 gas motor may be practicable under some circumstances ; 

 but what is really required is an arrangement that is non- 

 mechanical, and, at the same time, gives no back pressure. 

 There are a few appliances on the market that fill the bill 

 in this respect. 



An exhauster has become almost indispensable, even in 

 the smallest works, on account of the heavier holder 

 pressure that is now demanded. In the days of the flat-flame 

 burner and no day consumption, it was possible to get along 

 with a counterbalanced holder, giving 2o-tenths when the 

 weights were on and 25-tenths when unloaded. But with the 

 introduction of the inverted incandescent burner, pressures 

 of 35-tenths or more are called for at night, and if gas 

 cookers and engines are to have a good supply, there must 

 be 3o-tenths or so from 6 a.m. to dusk. The demand for 

 more supply pressure is general, both in large and small 

 towns, and the removal of the counterbalance weights from 

 the small holder synchronizes with the introduction of the 

 boosting fan at the outlet of the larger. The result is that 

 without an exhauster it is impossible to work with less than 

 6 to 8 inches on the retorts, whereas formerly it was possible 

 to get through the hours of daylight at least with about 

 4 inches. 



The difficulties in connection with running a boiler 

 and steam engine at a small works need not arise, because 

 the gasholder will supply the source of power. A small 

 gas engine and exhauster on one bed-plate take up very 

 little room, and the small amount of attention required i? 



