UNACCOUNTED-FOR GAS. 121 



at 70* will only measure out at 990 at 65, 980 at 

 60, 970 at 55, and so on. The bulk of the gas is 

 also affected by variations of the barometer, but as these 

 apply equally to all the meters, they do not affect the 

 question. Sometimes one meets with an impression that 

 a certain amount of condensation or reduction in bulk 

 takes place in the mains, apart from, and independent of, 

 reduction in temperature, and that gas will not measure 

 out so well at three miles from the works as it will close 

 by. A large deposition of liquid from the gas would be 

 attended with a loss in bulk, corresponding to the vapour 

 of such liquid, but under ordinary circumstances the 

 quantity of liquid taken from the various drip boxes will 

 not account for any appreciable percentage of the bulk of 

 the gas. The average temperature at a works meter will be 

 about 60, and that at the consumers' meters less than 50*. 

 The average temperature at a distance of 2 feet below 

 ground level, over the entire year, in the South of 

 England, is 48", and the larger proportion of the output 

 is supplied during the cold weather, perhaps 30 per cent, in 

 December and January. Many meters are situated in 

 cellars and other cold localities, so the average temperature 

 at which gas is actually sold will not greatly exceed 40, and 

 the loss from this cause, which is unavoidable, will be 3 to 4 

 per cent, on the sales. 



If there is any large amount of actual leakage, or escape 

 of gas from the inside to the outside of the pipes, at any 

 point between the works meters and the consumers' meters, 

 or through defective joints, the mains have not been skil- 

 fully or carefully laid in the first place, or perhaps corrosion 

 has taken place subsequently. Sometimes this is due to 

 some local cause, such as trade refuse liquids charged with 

 salt or acid coming in contact with the pipe, or through 



