SCIENCE IN RELATION TO THE ARTS. 207 



the most convenient, the cleanest, and the cheapest of heating agents, 

 and when raw coal will be seen only at the colliery or the gas-works. 

 In all cases where the town to be supplied is within say thirty miles 

 of the colliery, the gas-works may with advantage be planted at the 

 mouth, or still better at the bottom of the pit, whereby all haulage 

 of fuel would be avoided, and the gas, in its ascent from the bot- 

 tom of the colliery, would acquire an onward pressure sufficient 

 probably to impel it to its destination. The possibility of transport- 

 ing combustible gas through pipes for such a distance has been proved 

 at Pittsburg, where natural gas from the oil district is used in large 

 quantities. 



The quasi monopoly so long enjoyed by gas companies has had the 

 inevitable offect of checking progress. The gas being supplied by 

 meter, it has been seemingly to the advantage of the companies to give 

 merely the prescribed illuminating power, and to discourage the in- 

 vention of economical burners, in order that the consumption might 

 reach a maximum. The application of gas for heating purposes has 

 not been encouraged, and is still made difficult, in consequence of the 

 objectionable practice of reducing the pressure in the mains during 

 day-time to the lowest possible point consistent with prevention of 

 atmospheric indraught. The introduction of the electric light has 

 convinced gas managers and directors that such a policy is no longer 

 tenable, but must give way to one of technical progress ; new proc- 

 esses for cheapening the production and increasing the purity and 

 illuminating power of gas are being fully discussed before the Gas 

 Institute ; and improved burners, rivaling the electric light in brill- 

 iancy, greet our eyes as we pass along our principal thorough- 

 fares. 



Regarding the importance of the gas-supply as it exists at present, 

 we find from a government return that the capital invested in gas- 

 works in England, other than those of local authorities, amounts to 

 30,000,000 ; in these, 4,281,048 tons of coal are converted annually, 

 producing 43,000,000,000 cubic feet of gas, and about 2,800,000 tons 

 of coke ; whereas the total amount of coal annually converted in the 

 United Kingdom may be estimated at 9,000,000 tons, and the by- 

 products therefrom at 500,000 tons of tar, 1,000,000 tons of ammonia 

 liquor, and 4,000,000 tons of coke, according to the returns kindly fur- 

 nished me by the managers of many of the gas-works and corporations. 

 To these may be added say 120,000 tons of sulphur, which up to the 

 present time is a waste product. 



Previous to the year 1856 that is to say, before Mr. W. II. Perkin 

 had invented his practical process, based chiefly upon the theoretical 

 investigations of Hoffman, regarding the coal-tar bases and the chem- 

 ical constitution of indigo the value of coal-tar in London was scarcely 

 a halfpenny a gallon, and in country places gas-makers were glad to 

 give it away. Up to that time the coal-tar industry had consisted 



