284 



NA TURE 



[January 19, 1893 



•were originally determined from the other (yttrium tantalate). 

 In fact, it was stated in my former communication that the 

 Baddeleyite of Ceylon is itself associated with such a chemical 

 compound ; and I may add that this associated mineral was 

 there designated without the mention of a species-name because 

 it had been found to have a specific gravity (4'9) far below the 

 inferior limit (5 '5) hitherto observed in the case of undoubted 

 Yttrotantalite : it was intended to determine later whether or 

 not the lowness of the specific gravity was accompanied by a 

 difference in the proportion of the chemical constituents ; 

 further, the similarity of aspect of the zirconia and yttrium 

 tantalate of Ceylon is such that a confusion of the two would 

 be easy. In this way the discrepancy of the chemical results 

 and the complete accuracy of the observations of Dr. Hussak, 

 whose reputation stands so high in the annals of mineralogical 

 science, would be found consistent with each other. 



There remains the inconvenience that two names have been 

 suggested for the same mineral ; but according to the rules of 

 nomenclature formulated by Dana (rule 13^) the name of 

 Baddeleyite has the prior claim. I may add that the name 

 Brazilite was in use eight years ago, commercially at least, for 

 the specification of an oil-bearing rock found in the neighbour- 

 hood of Bahia. L. Fletcher. 



GAS POWER FOR ELECTRIC LIGHTING. 

 AT the ordinary meeting of the Institution of Civil Engineers 

 '^~*- on Tuesday, January 10, an interesting paper on " Gas- 

 Power for Electric Lighting" was read by Mr. J". Emerson 

 Dowson. The author stated that in Great Britain alone 

 gas-engines had been sold for electric lighting, exceeding 

 in the aggregate 7000 horse-power, and that in Germany 

 engines were used for about iioo arc- and 90,000 glow- 

 lamps. It was, however, only within the last few years 

 that gas-engines of large size had been before the world in a 

 practical form. The varying load-factor in central stations was 

 a serious trouble, and the author hoped to show that much of 

 the present loss, due to fuel, water, and wages, would be avoided 

 if gas-power were used instead of steam-power. 



Special reference was made to the central-station at Dessau, 

 belonging to the German Continental Gas Company. That 

 station was opened in 1886 with two 60 horse-power, one 30 

 horse-power, and one 8 horse-power (effective) engines, worked 

 with town-gas, and all the dynamos were driven by belting and 

 counter-shafts. In 1891 considerable alterations were made. One 

 60 horse-power engine, with its belting and counter-shaft, was 

 retained, and one of 120 horse- power introduced, coupled 

 direct to its dynamo. The speed of the engine and coupled 

 dynamo was 145 revolutions per minute, and the con- 

 sumption of town-gas was equal to 39 cubic feet per kilowatt. 

 Formerly, without accumulators, it was thought necessary to 

 adjust the size of the engines to the supply, so that they should 

 always be worked to their full extent. It had, however, been 

 found that a limited supply could more advantageously be fur- 

 nished entirely from accumulators. In spite of the loss of about 

 21 per cent, in the accumulators, large engines worked more 

 profitably in parallel than smaller ones supplying direct without 

 accumulators. Since February, 1889, the Municipality of 

 Schwabing, a suburb of Munich, had used an Otto engine 

 worked with Dowson gas for 10 arc- and 300 glow-lamps. The 

 load was variable, but with an average output of 22*5 kilowatts 

 per hour the fuel -consumption was 3-3 lbs. per kilowatt. The 

 town of Morecambe was lighted by nine arc-lamps and glow- 

 lamps, equal to i6oo of eight candle-power each, the dynamos 

 being driven by Stockport gas-engines worked with Dowson 

 gas. With an output of only 1155 kilowatts per week the 

 consumption of fuel was 2-58 lbs., and the cost of the gas, 

 including wages and fuel, was ^d. per kilowatt delivered. At 

 the chateau of Mr. Say, at Longpont, in the South of France, 

 there were 650 glow-lamps and one arc-lamp, supplied by a 

 dynamo driven by a Crossley engine worked with Dowson gas. 

 The consumption of fuel was i '2 lb. per indicated horse-power, 

 and 27 lbs. per kilowatt per hour. 



It was believed that the late Sir William Siemens first drew 

 attention to the fact, that when illuminating-gas was burnt in a 

 gas-engine to drive a dynamo, much more light was produced 

 electrically than could be produced by burning the same quantity 

 of gas in burners in the usual way. Latterly the consumption 

 of gas per horse power in gas-engines had been reduced, and the 



ratio was at the present time about 20 to i in favour of converting 

 the gas into an arc-light, by means of a gas-engine. The author 

 had collected data from various sources, as to the consumption of 

 ordinary town-gas by engines supplying electric light with and 

 without accumulators. The average of all the returns, with 

 engines under varying loads and without accumulators, was 

 about 47 cubic feet per kilowatt-hour ; when accumulators 

 were used, the consumption of gas was less, because the 

 engines then worked under a full load. With 47 cubic 

 feet per kilowatt, and 55 watts per 16 candle-power, one light 

 of that power required only 2 '6 cubic feet per hour; whereas 

 a standard Argand burner required 5 cubic feet per hour. In 

 this comparison, it was assumed that the glow-lamps and gas- 

 burners were in good order, but under ordinary working con- 

 ditions they did not maintain so high a duty. 



The question of load-factor was a serious one with any type 

 of engine, but with gas-engines the loss was much less than 

 with steam-engines. When a gas-engine was stopped, its 

 consumption of fuel stopped also, and there was no furnace 

 to maintain, nor was there any water to boil at starting. At 

 the same time, it was desirable that the gas-engine should be 

 worked as much as possible under a full load, and in this 

 respect the experience at Dessau was generally confirmed. 

 A central-station was worked under trying conditions, and in 

 the London district there was only a full output of current 

 during from three to five hours in every twenty-four ; moreover, 

 about 60 per cent, of the total output was required during that 

 short period. In practice, this meant that in a station where 

 the current was supplied without accumulators, the engines 

 were run at a reduced speed during a portion of the time, and 

 at other times some of them were stopped altogether ; but all 

 had to be ready to work in the evening, and occasionally in the 

 day-time, when there was fog. Generally, it might be assumed 

 that the average consumption was more than 6 poucds per 

 kilowatt where accumulators were used, and about 9 to 12 

 pounds where they were not used. In any case, with the best 

 possible arrangement of steam-power, there must be a large 

 amount of fuel consumed which did no useful work ; for, even 

 if some of the fires were drawn, they had to be re-lighted, and 

 the large quantity of water which had cooled during the time of 

 standing must be re-heated. 



The author believed that the solution of the difficulty was to 

 be found in the use of gas-plant instead of steam-plant. With a 

 large gas-engine, one brake horse-power per hour could be 

 obtained with a consumption of about i lb. of anthracite, or 

 i/j lb. of coke; whereas the consumption of coal with the 

 steam-engines used for central-stations, must be taken at about 

 2,\ lbs. per brake horse-power, when working under a full load. 

 a" saving of not less than 50 per cent, could therefore be effected 

 in stations where the engines were fully loaded ; and where 

 there were great fluctuations in the output, the loss of fuel with 

 boilers not used, or only partly used, could be almost entirely 

 avoided. For a maximum of 400 kilowatts, there would be 

 three gas-generators, each capable of supplying one-third of 

 the maximum required. The production of gas could be raised 

 or lowered in several ways, and the working of each generator 

 could be stopped immediately by shutting off its steam supply. 

 Supposing, therefore, that all three generators were working 

 at their maximum rate, and a gradual reduction was required, 

 this could easily be effected ; and when the production of one 

 or two generators could be dispensed with their operation 

 was at once stopped. The third generator could then be kept 

 at work, and its production adjusted to suit the minimum con- 

 sumption required. A gas-generator had a small grate-area 

 compared with that of a boiler, and much less cooling-surface ; 

 it contained no water, and required no chimney-draught. A 

 generator of the size referred to lost only 6 to 8 lbs. per hour 

 whilst standing. If an average of only 40 per cent, of the maxi- 

 mum power were jequired for twenty-one hours, it was equivalent 

 to letting two of the generators stand for that period ; and at 

 8 lbs. each per hour that meant a total loss of only 3 cwts.; 

 compared with the much greater waste when steam-power was 

 used. As the use of large engines, driven with generator 

 gas, was of recent date, the author proceeded to describe the 

 gas-plant used, and gave the results of engines working regu- 

 larly with Dowson gas, under the usual conditions obtaining 

 in factories. .He also gave the results of brake- tests made 

 with several engines of large size, and reproduced indicator 

 diagrams taken from engines of different makers. Although 

 admirable results had undoubtedly been obtained from engines 



NO. 



12 12, VOL. 47] 



