i8o POPULAR SCIENCE MONTHLY. 



pipe surface, and barometric and thermometric variations. The trans- 

 mission of gas causes, therefore, a loss of candle power ranging from a 

 small fraction to several candles, although it is possible to conceive of 

 conditions so extraordinarily favorable that the illuminating quality 

 of the gas might be actually improved by distribution. 



It will be readily understood from this explanation that tests made 

 at the gas works, or even at points arbitrarily selected at a certain 

 distance from these works, are hardly calculated to satisfy the con- 

 sumer. For this reason I have preferred, in conducting these tests, 

 to sacrifice to some degree the accuracy that obtains in laboratory 

 experiments, in order to test gas samples taken from the main directly 

 in front of the complainants own premises. I argue that the consumer 

 cares little or nothing as to whether the gas as manufactured complies 

 with the law, or whether tests made at a point perhaps a mile away 

 from the works show the required candle power; but that he does 

 want to know what is the quality of the gas passing in at his service 

 pipe. The method of collecting and transporting to a laboratory the 

 gas samples enables one to say with positiveness that the gas at the 

 point of complaint has an illuminating power of at least so many 

 candles, and that it may be even one candle better than the tests 

 indicate. The figures thus obtained range from twenty and a half to 

 twenty-five. So, then, the gas delivered to the consumer is not 'poor.' 



Hygienic reasons demand that the impurities in the gas shall not 

 exceed a definite percentage. Whatever effect these impurities may 

 bave upon the candle power has been covered by the tests above ex- 

 plained, so that any further consideration of these impurities may be 

 omitted here. 



It is always a difficult matter to convince an indignant householder 

 that the quality of the gas supplied to him is satisfactory. He knows 

 perfectly well that he is not getting the desired result, and no explana- 

 tion, however elaborate, as to candle power will placate him, unless it 

 be supplemented by a further statement detailing the cause of the 

 trouble. When you are trying to draw water in the bathroom while the 

 cook is filling the washtubs in the basement, do you say the water 

 is 'poor'? Why, then, should you characterize the gas as 'poor,' 

 when people nearer to the gas works than you are happen to be draw- 

 ing heavily upon the common gas main? Imagine, if you please, a 

 long gas main, with consumers tapping in at points throughout its en- 

 tire length, and with a gas holder forcing the gas in at one end. Since 

 there is a loss of pressure, caused by the transmission, it follows that 

 the pressure will be higher at the gas holder than anywhere else along 

 the line, the difference in pressure depending, roughly, upon the size and 

 length of the pipe and upon the amount of gas flowing. Now, for any 

 one customer the size and length of pipe will remain constant, but the 



