8o 



SCIENTIFIC NEW^S. 



[April 20, 18 



The amount of radiant heat given out by a regenerative 

 burner is considerable close to the lamp, but rapidly 

 diminishes as the distance from it increases, so that five 

 feet from the burner of the lamp it is hardly perceptible, 

 and only amounts to about 2-ioths of a degree; and this 

 may be entirely done away with by suspending a sheet 

 of thin plate glass just below the lamp, which, while 

 cutting off the heat-rays, will allow 88 per cent, of the 

 light to pass through. 



THE INSTITUTION OF CIVIL ENGINEERS. 



At the ordinary meeting on Tuesday, the loth of April, 



< the President, Mr. Bruce, being in the chair, the paper 



read was on " Compressed Oil-Gas and its Applications," 



by Mr. Arthur Ayres, M.Inst.,C.E. 



In considering this system of illumination, its applic- 

 ability to buoys, isolated beacons, lighthouses, and rail- 

 way carriages, etc., the author treated it under the 

 primary heads of mode of manufacture, illuminating 

 properties, cost, storage, and transit, and in doing so he 

 referred to the early history of oil-gas and the patents 

 taken out from time to time in connection with the 

 system. It was stated that in 1825 Faraday contributed 

 a paper to the Royal Society " On New Compounds of 

 Carbon and Hydrogen, and on certain other Products 

 obtained during the Decomposition of Oil by Heat." 

 That communication, however, dealt with the chemistry 

 of oil-gas. It was mentioned in that paper that i,oqo cubic 

 feet of good gas yielded nearly one gallon of hydro-carbon. 

 The gas from which the hydro-carbon was obtained was 

 manufactured by the Portable Gas Company, and was 

 compressed to thirty atmospheres. It was drawn from 

 a gasholder and passed over water into a large and 

 strong receiver, and from it into portable vessels, the 

 principal condensation taking place in the receiver. 

 The oil-gas manufactured by the Portable Gas 

 Company was not distilled from shale oil or petroleum, 

 but from other oils and fatty substances, mineral or 

 vegetable. Between the years 1792 and 1883 numerous 

 ingenious patents were taken out for manufacturing and 

 compressing oil-gas for lighting and heating purposes. 

 Oil- or hydro-carbon gas was the product of heavy petro- 

 leum or shale oil once distilled. It had a specific gravity 

 of about "840, and flashed at about 220'' Fahrenheit. In 

 detaihng the process of the manufacture of oil-gas, the 

 author described the works erected at the South Fore- 

 land by Pintsch's Patent Lighting Company (Limited). 

 The illuminating intensity of oil-gas might be taken at 

 from forty to fifty candles when burned in a London 

 standard argand burner, with a consumption of five cubic 

 feet per hour, under a pressure of 0-5 inch of water. 

 Until the adoption of oil-gas for their illumination, buoys 

 and isolated beacons were only useful for the purposes of 

 navigation by day ; but they were now equally so by 

 night (in clear weather), enabling vessels to navigate 

 with safety intricate channels, which hitherto could not 

 have been attempted escept at considerable risk. Gas- 

 buoys, as at present used by the Honourable Corporation 

 of Trinity House, were constructed of best mild steel ; 

 they were spherical, nine feet in diameter, and sur- 

 mounted by a light wrought-iron superstructure, carrying 

 a lantern enclosing the illuminating apparatus. The 

 total weight of one of these buoys complete was about 

 80 cwt., the weight of the buoy being 78I cwt, and that 

 of the illuminating apparatus i^ cwt. The buoys were 

 usually charged to a pressure of five or six atmospheres. 



or from 75 to 90 lbs. pressure per square inch. The- 

 gas was contained in the spherical portion of the buoy, 

 the capacity of which was about 382 cubic feet, and was 

 consumed at the rate of three-quarters of a cubic foot per 

 hour, burning night and day continuously. When fully 

 charged to five atmospheres, and burning at the above 

 rate of consumption, the light would be maintained for 

 106 nights and days. The intensity of the light was from 

 seventeen to twenty candles tnrough the lens. There 

 were now 214 buoys, lightships, beacons, and other 

 lights in use in various countries on Pintsch's system. 



The author next dealt with the application of com- 

 pressed oil-gas to the lighting of railway carriages, which 

 he stated was one of growing importance. It was prob- 

 ably first tried in the year 187 1 with satisfactory results, 

 in Germany, on the Lower Silesian Railway, and in 

 England in 1878 on the St. John's Wood trains of the 

 Metropolitan Railway, with equally satisfactory results. 

 The Great Eastern Railway Company was the next to 

 adopt it, the Metropolitan Railway Company definitively 

 adopted it for the whole of its rolling-stock a few weeks 

 later, and other Companies quickly followed suit. The 

 systems chosen were those of Messrs. Pintch and Messrs. 

 Pope and Sons, which differed but little from each other. 

 Some trials were also made of Messrs. Bower's system 

 on the Great Northern Railway. The gasholders were 

 attached either to the roofs or to the under-framing of 

 the carriages, and were charged to a pressure of from six 

 to eight atmospheres. The gas was conveyed to the 

 roof-lamps by pipes from the gasholders, passing through 

 a contrivance for regulating the pressure at the burners,, 

 one such regulator being attached to each carriage. There 

 were now 23,499 carriages so illuminated on Pintsch's 

 system, and 2,791 on Pope's system. In the double 

 journey between Euston and Aberdeen the cost of the 

 ordinary oil system was 8| times more than oil-gas. 



MODERN PHOTOGRAPHIC ENGRAVING 

 AND PRINTING.— in. 



A Paper by Mr. George S. Waterlow, read at the 

 Conference of the Camera Club. 



(Continited frojn page 3S7-) 



WE now come to collotype printing, and it is perhaps 

 of all methods of photo-mechanical printing the one 

 which lends itself to the greatest variety of effects ; every 

 one of the previously-mentioned processes can be closely 

 imitated by it. 



It is, above all others, the best process for facsimile 

 reproductions in large numbers, reproducing an engraving, 

 a fine drawing, a wash drawing, a photograph of nature, 

 or from life, all with equal facility. The principle of the 

 process is, as in the others, founded upon the altered 

 nature of gelatine with bichromate of potash after ex- 

 posure to light, but in this case differing from those 

 mentioned previously in the fact that the printing begins 

 and ends with the original gelatine surface. It is very 

 simple — a thick sheet of plate glass (sometimes metal is 

 used) generally, but not necessarily, ground on the sur- 

 face, is first coated with a substratum containing silicate 

 of soda and albumen (15 to i) which has a great holding 

 power ; when this coating is dry, the surface is recoated 

 with a solution of gelatine and bichromate of potash, and 

 dried quickly in a hot dark room, or chest. The plate is 

 now ready for exposure under a negative (either a collodion: 



