18 Transactions of the 



a low temperature. The testing engineers report that there was no 

 apparent loss of illuminating power. The furnace and retorts at 

 Battersea are very compact, occupying the space of an oi'dinary engine 

 of about 30-horse power. These retorts are only in use two hours out 

 of the twenty-four, and it is estimated, if at work all day, they are 

 quite large enough to supply a small town of 4,000 inhabitants. As 

 regards the most important bearing of saving of manual labour, it is 

 found to amount to dispensing with the services of 29 out of 30 of 

 labourers required in the old coal distiUation process. 



AIR GAS. 



The second new gas is called the " Air Gas ;" it is patented by 'a 

 Company called the Air Gas Light Company (Limited.) 



Its preparation is even simpler than that of the former gas. It is 

 made thus, on a small scale: Atmospheric air is forced through a 

 bottle containing Hydro-Carbon Oils ; the patentee's secret consisting 

 in the proper mixture of these. In fact, it appears that it is the 

 vapour of this mixture that burns, the air being used only as a means 

 of carrying the vapour. The great advantage it has is that it 

 can be made in the house, and is very applicable for country houses, 

 the apparatus being so simple and occupying so httle space, that a 

 servant of ordinary inteUigence can ^\ork it easily. The apparatus 

 costs £7 only, and is able to supply 25 burners. The inventor claims 

 that 1,000 feet of his gas are equal to 2,000 feet of coal gas, and it 

 can be produced at a cost of about 1/3 per 1,000 feet. It is, 

 therefore, very much cheaper than coal gas. 



In the " Hydio-Carbon Gas" a certain quantity of coal is necessary, 

 although but httle, while in the "Air Gas" none is used whatever. 



NEW COAL GAS EETORTS. 



I wish now to mention an improvement in the making of coal gas. 

 Ill the process now in use the outside of the coal gets heated and 

 bums before the centre of the coal does, so that a great deal of the 

 available gas is wasted. A patent has been taken out for the foUo-^ving 

 machine. An ordinary gas generating retort is taken, and fixed 

 upright in the furnace ; through it runs a long spiral screw, which is 

 kept'^turning by some very simple machinery. It is a self-feeding 

 machine, having to be supplied Avith small coals about twice a day. 

 The screw keeps turning, and thus exposes the Avhole of the coals by 

 turns to the heat of the furnace. The coal finds its way down by 

 degrees to the other end, and having had all its gas extracted, falls 

 into cold water. This process, it is found, extracts the gas much more 

 thoroughly from the coal, and that a mujh greater quantity of gas is 

 obtained by this than by the old process, and it is also of a better quality. 



The advantages, then, appear to be — 



First— "Ta-cki. the gas is extracted thoroughly from the coal, and an 

 increased quantity of gas of a superior quality is obtained. 



Seconclbt — That as it works almost automatically, more than half of 

 the manual labour can be dispensed with. 



