32 CONSTRUCTION AND MANAGEMENT OF SMALL GASWORKS. 



sort, because the desired result can be accomplished, by 

 a few trees judiciously placed, in a much less prominent 

 and more natural manner. Trees are never an eyesore, and 

 they do not attract attention and set people wondering what 

 there is behind them. 



A special feature with the old school was that the gas- 

 works should be situated in the lowest part of the 

 district. This certainly has the advantage of rendering 

 it practicable to work with a lighter holder pressure ; which 

 was a more important consideration in the days of the flat- 

 flame burner than it is at present. Seeing that ordinary 

 coal gas in mains takes up an additional inch of pressure for 

 a rise of 100 feet in respect to altitude, and loses to a 

 corresponding extent for a fall to the same extent, it follows 

 that the pressure in parts of the district 100 feet above the 

 level of the works may be, but not necessarily so, during 

 the times of heaviest consumption, actually higher than that 

 at the inlet of the governor. I know a district three miles 

 from the works, and over 100 feet higher above datum 

 line, and the gain of pressure due to the rise is greater than 

 the loss represented by the pressure required to carry or 

 drive the gas, with the result that the pressure at the far end 

 is higher than at home. The converse, of course, applies. 

 If a part of the district is lower than the works, extra 

 pressure must be applied to force the gas down the hill. 

 The rule, of course, like all others, must be applied with 

 judgment. It does not pay to keep the whole of the 

 district under an excess of pressure in order to ensure that 

 half a dozen customers living in a valley should get enough. 

 The low parts of the district are apt to be boggy and subject 

 to flood, which means extra expense for foundations and a 

 risk of operations being stopped and the property seriously 

 damaged, by sudden flooding of the furnace ash-pits, the 



