LAYING OUT THE DESIGN OF WORKS 47 



material with tar. The thinner liquid thrown down towards 

 the outlet end, flowing back to the hydraulic, serves to 

 dilute the more viscid matters that are first deposited, and 

 to carry them freely through to the store well. 



There is usually a demand for fairly uniform candle-power. 

 Weak pressures and small pipes in various parts of the dis- 

 trict throw into prominence a comparatively slight variation 

 in illuminating power. But cannel or high-class coal is 

 sometimes used as much for thinning the tar in the hydraulic 

 and condenser as for keeping up the illuminating power. I 

 once met with a small works so deficient in this respect that 

 only cannel coal could be used. When a good brand of 

 bituminous coal was tried, as a matter of economy, and to 

 prevent the smoke and soot due to excessively rich gas, the 

 result was a complete breakdown. 



In the large works there is no question as to the removal 

 of the whole of the ammonia, because it is a source of 

 profit. But when the works is so small that a sulphate plant 

 is out of the running, and any small sum obtainable from a 

 neighbouring gasworks for the liquor barely covers the cost 

 of cartage and carriage, there is a disposition to regard 

 ammonia simply from its capability or otherwise of adding to 

 the profits, and to overlook the fact that it is also an objec- 

 tionable impurity. It acts powerfully on copper and brass, and 

 when any appreciable proportion is allowed to remain in the 

 gas, the water in the gasholder tanks becomes charged to a 

 sufficient extent to corrode the holder. There will also be 

 frequent complaints of stiff taps and hinge joints from the 

 consumers, and the meters will be affected. So, even if the 

 liquor has to be given away, it is desirable to extract the 

 ammonia from the gas, and, in so doing, to utilize its 

 purifying capabilities, especially so as it means a reduction 

 in the other impurities and in the cost of running the dry 



