Feb. lo, iSSi] 



NA TURE 



351 



Narrow ^harijl) -defined rajs were lemarked to shoot up on 

 several occasions from the horizon ; these gradually wideaed 

 out, losing their sharp boundaries and becoming less distinct, 

 some times behaving like the cloud-like masses or becoming in- 

 tensified by a *' brush di^charge " occurring across them; at 

 others they faded gradually away. 



At about 12.30 they had all disappeared, but a bright glow to 

 ilie north horizon and faint glows at intervals over the sky 

 between north and west. 



It was not observed how far the discharges extended eastward. 



24, Wa'erloo Road, Dublin Gerard A. Kinahan 



The following details of this evening's remarkable aurora 

 uiiy be of intere.it to your readers. At 6.45 p.m., while the 

 new moon was setting, there \\'as an appearance of a belt of 

 luminous white cloud reaching along the northern and north- 

 western horizon, giving indications of a tendency to divide into 

 two separate parts, of which the western one had its upper 

 surface parallel v\ith the horizon, but that to the north was 

 arched. From both parts rays and vertical bands of white light 

 began to shoot upv\'ards, reaching nearly to the zenith, and 

 becoming more and more distinct, especially in the north (as 

 oppo-ed to the north-west), and one long feathery streamer was 

 very conspicuous, and reached in a slanting direction from a 

 point o\\ the horizon immediately under the Pole Star up to 

 Capella. 



In the meantime the cloud-like appearance to the north-west 

 had spread upwards over the heavens and assumed a dark ruddy 

 colour, which gradually became brighter and more rosy, until it 

 exactly resembled the light of dawn or sunset, which is s mietimes 

 reflected on the opposite side of the sky to the ri,ing or setting 

 sun. At this time the northern heavens became suffused with 

 white light extending over the space where the bands and rays 

 had been appearing, which throbbed repeatedly and vividly like 

 the electric di-chirge in a vacuum tube, continuing some minutes. 

 This gradually faded away, and the pink light to the north-west 

 also disappeared by degrees, so that within twenty or twenty-five 

 minutes fi'om the commencement (say at ab^ut tive or ten minutes 

 past seven) there was little to be seen but a hardly noticeable 

 light along the north horizon. F. Horner 



Mells Park, Somerset, January 31 



It may interest your readers to know that the anror 1. of 

 January 31 was distinctly seen by me here at abiut seven o'clock 

 on that evening. Such a .sight is so unciimmon in this part of 

 London that I had some difficulty in convincing my friends that 

 It was the aurora. As I walked down the Wickham Road, 

 Brockley, towards Greenwich, broad bands of light shot up from 

 the northern regions and reached nearly to the zenith. Descend- 

 ing amongst the fog and smoke that overhung the lower parts of 

 New Cross, the light gradually faded, and I saw no more of it. 



W. J. Spratung 



Aske's Hatcham Schools, Hatcham, February 4 



The aurora of January 31 was well seen here. It was at its 

 brighter at 6.40 p.m. It extended from about north-west to 

 nearly east. In the north-west and to the north of the crescent 

 rnooa there was a large irregularly shaped patch of greenish 

 phosphorescent light. Then round from it towards the north 

 rose crimson streamers towards the zenith. The streamers con- 

 tinued round to the east nearly, still ascending zenithward, but 

 white rather than crimsoa, between northeast and east. The 

 streamers changed every instant, but the large greenish patch of 

 light in the north-west was steady for some miimtes. 



It would be interesting to know whether observers in America 

 noticed any unusual solar activity at the same absolute time as 

 the aurora was occurring here, and also whether the magnetic 

 elements in both hemispheres (north and south) showed disturb- 

 ances in sympathy. D. Traill 



Raleigh Lodge, Exmouth, February 4 



GAS AND ELECTRICITY AS HEATING 

 AGENTS^ 

 XL 

 r^ AS engineers have been under the impression until now that 

 ^-^ a supply of cold air was favourable to the production of a 

 brilliant flame. This is a misconception, which was very general 

 also as regards the combustion of solid fuel in furnaces, until 



■ A lecture by C. William Siemens, D.C.L., LL.D., P. R.S., on January 

 27. in St. Andrew's Hall, Glasgow, under the auspices of the^ Glasgow 

 -Science Lecture Association. Continued from p. 329. 



it was disproved by Stirling, by Nellsun, and liy the introduc- 

 tion of the Regenerative Gas Furnace. The " duplex burner " 

 owes its brilliancy to the heating effect of the one burner upon 

 the other ; and my brother, Mr. Frederick Siemens, has more 

 recently c instructed a burner in which the flame of the gas is 

 reversed in its action in order to heat in its descent the ascending 

 current of flame-supporting air. 



By the ap])lication of the principle of conduction before 

 described, I obtain the hot-air current in a most simple manner 

 without interfering with the free action of the flame. The 

 construction of my burner will be seen from the diagram. 

 A is an ordinary Argand burner, taking its supply of gas 

 through the enlarged vertical copper tube B. 'This copper 

 pipe terminates in a rjd c of highly conductive copper, which 

 passes upward through the burner, and carries at its top a ball 

 of porcelain or other refractory material. The rod is coated 

 with platinum or nickel to prevent oxidation when heated 

 (almost to rednes-) by the heat of the flame. The tube i) is 

 armed with radial plates of copper pre-entinj a considerable 

 aggregate surface, and abutting externally against a covering of 

 asbestos or other non-conductive material. 



The waste heat of the flame, or that portion of the heat 

 produced in combustion which is not utilised in luminous rays, 

 serves to heat the ball of refractory material D and the conduc- 

 tive rod c. The heat is thus transferred by conducti an to the 

 tube B, with its laminar radii, between the extensive surfaces of 

 which currents of air are free to ascend toward the Argand 

 burner. The air is thus heated to from 700° to 8o3° F. before 

 meeting the gas, and the ultimate temperature of the flame is 

 increased to at least the same amount, causing a larger propor- 

 tion of the heat developed in combustion to reach the point of 

 luminous radiation. 



But not only the quantity of light but its quality is improved 

 by the higher temperature obtained. 



It may appear surprising, but it is a fact susceptible of ac- 

 curate proof, that the light obtained in consumption of a given 

 amount of gas may thus be increased by some 40 per cent., and 

 that in this large proportion the deleterious influences connected 

 with gas lighting may be diminished. Gas will thus be better 

 able to hold its position against its more brilliant rival the 

 electric light, except for such large applications as the lighting 

 of public halls and places, of harbours, railway stations, ware- 

 houses, &c , for which it is pre-eminently suited. Add to these 

 improved applications of gas the ever-increasing ones for heating 

 purposes, and I have only to express regret that I am not a gas 

 shareholder. 



If gas is to be largely employed, however, for heating pur- 

 poses, it will have to come down in price ; and considering that 

 heating gas need not be highly pu ified, or pos-essed of high 

 illuminating power, the time will 'come, [I believe, when we 

 shall have°wo services, one for illuminating, and the other for 

 heating gas. 



In many towns two .systems of gas mains already exist ; and 

 it would only be necessary to appropriate the one for illumina- 

 ting and the other for heating gas. The ordinary retorts could 

 be used for the production of both descriptions of gas, it being 

 well known that even ordinary coal will give up gases of high 

 illuminating power during a certain portion of the time occupied 

 in their enfire distillation. The gases emitted from the retort 

 when fir^t charged are to a great extent occluded gases of low- 

 illuminating power such as fire-damp or marsh-g.as, and these 

 should be turned into the heating mains. In the course of 

 half-anhour these occluded gases, together with the aqueous 

 and other vapours, will have left the coal, which is then in the 

 best condition to evolve defiant gas and other gases rich in 

 carbon, and therefore of high illuminating power. The period 

 during which such illuminating ga-es are emitted extends over 

 probably two hours, after which the retorts should again be 

 connected with the heating gas mains, until the end of the 

 process. The re-ult of this modus operandi would be that the 

 illuminating gas supplied, say in London, from Newcastle coal 

 would probably exceed 20 candle ])ower, instead of 16 as at 

 present, whereby the objectionable results of gas lighting would 

 be greatly diminished, and there would be, say, an equal 

 volume of heating gas available, consisting for the most part 

 of mar-h-gas, which, although greatly inferior to olefiantgas in 

 illuminatiiig effect, would be actually more suitable for heating 

 purposes, because less liable to produce soot in its combustion. 



The total cost of production would not be increased by this 

 separation of the gases, and the price might with advantage 



