January 6, 19 16] 



NATURE 



523 



1- temperature of the air, and there was even a 

 ndency for jjetrol to condense in the pipes during 

 id weather. These defects should not exist in 

 > trustworthy type of modern 

 ichine. 



The chief elements in a petrol- 

 ; gas plant are the carburetter, in 

 ., hich the desired mixture of petrol 

 c'lnd air is produced; the holder in 

 which the gas is stored ; and the 

 compressor for the purpose of driv- 

 ing the gas through the pipes. The 

 motive power may be supplied by a 

 falling weight, hot-air engine, or 

 water power. For country-house 

 lighting, the falling weight is 

 usually preferred on account of its 

 simplicity. A trustworthy plant 

 should operate quite automatically, 

 yielding the same quality of gas, 

 however man}' lights are turned on 

 (within the limits of the plant), and 

 >b.ould require little or no attention 

 ' vond filling up with petrol when 

 cessary and occasionally winding 

 1 the weight. 



A technical point of some interest 

 i- the percentage of petrol which it 

 i- desirable to include in the gas. 

 In some cases, for example in the 

 "County" petrol-air gas system, the 

 comparatively rich mixture of 6 per 

 cent, is preferred, and it is con- 

 sidered that this enables the plant 

 to be designed and operated on 

 highly scientific lines, and that it is 

 of value in enabling a mixture of 

 ^^ constant composi- 



^^ tion to be ob- 



tained, as well as 

 , desirable in the 



•IV interests of safety. 



vm'^\ 111 Other well- 



10, \ known makes, for 



I I ( \ example, the Wil- 



I 1 1 \ lett system, the 



f \ \ percentage of pet- 



new mantles. In favourable circumstances 100-120 of 

 these lights can be run for a consumption of one 

 gallon/ of petrol per hour. A small plant, feeding 



— ferrol from l'a(U( 



0ft<5 .. .. o— 



Fig. 30.— Sectional view of "County "petrol-air gas plant. In this diagram thrre types of arrows are used 

 b paths taken by the air, petrol, and the resulting gas. The plant consists in t 



the 



rol is 

 oniv. 



per cent. 

 This is 



stated to operate 

 quite satisfac- 

 torily, and it is 

 also' claimed that 

 ordinary motor- 

 car petrol can be 

 used, and that no 

 special variety of 

 lighting spirit is 

 r'H|uired. 



\ petrol-air gas 



-rem enables 

 1 lights to be in- 

 sialled perman- 

 ently in position 

 and used either as 

 central or units or wall brackets. The ordinary type of 

 inverted burner used is of the Bijou type, from which 

 as much as 70-80 candle-power may be obtained with 



NO. 2410, VOL. 96] 



Fl(i. 3.— General 



denote the respective paths . ... 



main of two ci pper bells working in water seals, the smaller of which acts as an air pump whilst the 

 larger constitutes the holder for the gas as it is made. The air-pumping bell is made to rise and fall 

 by means of the weights and on its upstroke takes in air through the valve T. On reaching the top of 

 its stroke it is disengaged from the action of the weights (which are then held stationaiy), and the valve 

 T closing, the air-bell falls by its own weight and drives air down the central pipe K into the larger 

 bell via the pipe L and the annuins F. Before reaching the larger bell, however, it is caused to pass 

 close along the surface of the carburetter by the baffle plate I. The petrol is delivered on to the sur- 

 face of the carburetter by the petrol pump G in small amounts (a teasponnful or so at a time) along the 

 small pipe P. The petrol pump G, being attached directly to the air-bell, makes stroke for stroke with 

 it, thus ensuring that air is never delivered without its complement of petrol under any conditions of 

 running. The gas is delivered to the service down the central pipe at N. 



10-20 lights, would probably cost about 25i.-35/. 

 A larger size, capable of supplying 100 lights, 

 about 100Z.-120J. The complete cost of light- 

 ing installation, including plant, piping, and 

 simple fixtures, would probably work out to 

 betv^-een two and three times the above figures. 

 Much, however, depends on the expenditure on 

 fittings and the shed for housing the plant, and 

 the distance from which materials have to be 

 supplied. Prices have naturally been affected 

 somewhat by the war. A consumer should re- 

 member that in remote places it is not always 

 easy to get prompt technical assistance, and 

 should therefore be careful to select a thoroughly 

 up-to-date and trustworthy make of machine, 

 even if somewhat more expensive than others 

 on the market. 



The above remarks have referred mainly to 

 the use of petrol-air gas plants for country 

 houses, but there are also opportunities for its 

 use in small workshops, laboratories, etc. It 

 has also been used occasionally for military 

 camps and even for village lighting, V 

 in such cases the nature of the area to be covered 

 has an important bearing on the method of illumina- 

 tion supplied. In a large and scattered area the 



>f ' ' County " petrol-air gas plant 



