July 2 2, 1880] 



NATURE 



167 



account of the notices that have appeared in Nature (vol. xxi. 

 pp. 330, 372, and vol. xxii. p. 77) and in Comptes rendus (xc. 622- 

 26), this note would be needless, were it not that some may regard 

 these ashes as of recent origin. 



Microscopically the material (already described by Prof. 

 Delesse) is seen to be decomposed to a considerable extent. The 

 materials evidently filled an old crater, and have been subjected 

 to secondary action, so that of the original constituents only the 

 feldspar and augite are left. The other constituents are the 

 results of the alteration of this andesitic (probably) debris. _ No 

 trace of rc-cent volcanic material could be found in that examined 

 by me. In no sense can these ashes be called a recent product ; 

 they have simply been transferred from one place to another. 

 The transfer is recent, but the ashes have for ages been at or 

 near the surface of the earth. M. E. Wadsworth 



Museum of Comparative Zoology, Cambridge, 

 Mass., U.S.A., June 30 



Large Meteor 



On Friday evening last, July 9, at gh. 45m., I saw a very fine 

 meteor about equal in brightness to Venus at her maximum, 

 moving very slowly from nearly west to south-west. I did not 

 see its origin. It passed about 4° above Spiai, and disappeared 

 soon afterwards, as nearly as I could estimate, in altitude 16° 

 and azimuth 50° west of S. Its apparent course was only 

 slightly inclined to the horizon, approaching it at an angle of 

 about I in 10. 



Its apparent angular velocity was about S° in a second, its 

 light yellowish till the moment of extinction, when it became 

 blue and fainter, and disappeared without any sign of explosion. 

 Its course was somewhat wavy, and the trail it left behind it 

 very evanescent. My latitude and longitude was 51° 25' and 

 0° 14' W. F. C. Penrose 



Coleby Field, Wimbledon, July 14 



Ball Lightning 



On Saturday night, the 17th inst. , an instance of this form 

 of lightning came under my observation. 



The day had been hot, the thermometer registering a tempera- 

 ture of about 71° F. in the shade during the middle of the day, 

 which was bright and clear. In the evening, however, a curious 

 haze or mist spread rapidly over the landscape, while the tem- 

 perature had fallen to about 68° F. This haze was very much 

 denser and more analogous to the smoke-fog of a town than I 

 have ever observed in the country at this time of year, yet the 

 air did not seem particularly damp or chill. 



About 9 p.m. frequent flashes of sheet-lightning occurred, 

 with rumblings of distant thunder at intervals, both of which 

 continued more or less up to midnight, about which time, the 

 mist having somewhat cleared off, I saw when returning home, 

 apparently about a quarter of a mile ahead, a ball or globe of 

 fire of considerable size descend slowly from the clouds, and 

 when near to or touching the earth suddenly disappear, its 

 disappearance being accompanied by two slight but quick con- 

 cussions, which may have been an explosion and its echo. The 

 fire-ball could not have been visible more than five or six seconds, 

 I cannot ascertain that any damage was done by it. 



As this somewhat rare and curious phenomenon seems to be 

 manifesting itself at this period, accompanying the thunder- 

 storms we are having (see Nature, vol. xxii. p. 193), may I be 

 permitted to suggest that those interested in electrical science 

 should be on the alert to observe any repetition of the occurrence 

 with its concomitant circitmstances ? W. F. Smith 



Sutton Valence, Kent 



E. M. F. should read Prof. Ayrton's Sheffield lecture on 

 " Electricity as a Motive Power " (see Nature, vol. xx. p. 568) ; 

 any decent text-book — Noad's, for example — will tell of the 

 older attempts of Jacobi to propel boats by electricity. 



THE RECENT EXPLOSIONS 



A LTHOUGH it is difficult to say anything new on 

 ■^*- the subject, or give instructions more effective than 

 such as have been given over and over again, still the 



recent remarkable and destructive explosions in London, 

 Wolverhampton, and Monmouthshire seem to call for 

 some remarks at our hands. 



Two serious explosions of gas foUovping close on 

 each other, in the streets of large towns, announce to 

 every one that the difficulties of supplying gas to large 

 numbers of consumers have not been completely over- 

 come. 



The special feature in the London accident was the 

 occurrence of a series of explosions, at first at nearly 

 regular, and then at increasing intervals, along the gas 

 main. The first explosion blew out the "cap" of the 

 main with great violence ; the rush of heated air, doubtless 

 mingled with more or less gas, in the other direction 

 seems to have carried the flame — probably by a rapidly 

 occiu-ring series of small explosions — to a point at which 

 a mass of explosive gas was again reached and fired. 

 The mass of gaseous mixtute fired in the second ex- 

 plosion appears to have been about equal to that in the 

 first, but towards the close of the series either the gas 

 became much more diluted with air, or the air became 

 much more charged with gas. It seems just possible that 

 vibrations propagated by the first explosion passed rapidly 

 through a gaseous medium, consisting of much air and 

 little gas, until they came in contact with a mass of gas 

 and air, which they threw into rapid vibration; and so 

 caused to explode. But from the experiments of Abel 

 and others one would scarcely expect this to occur under 

 the conditions which — ^judging from the evidence given 

 at the inquest — appear to have existed. 



A second point, illustrated more markedly by the 

 Wolverhampton explosion, is the apparent readiness with 

 which a soil may be charged with coal-gas and retain this 

 gas for long periods of time. The passage of such gas 

 into drain-pipes, and perhaps even into unfilled gas-mains, 

 seems to be of ready occurrence. 



Experiments might well be instituted by the gas com- 

 panies to determine the power of soils for absorbing and 

 retaining coal gas, and secondly, the conditions of diffusion 

 of mixtures of gas and air through the walls of pipes of 

 different materials. If it can be shown with certainty 

 that the valve at the junction of the main in which the 

 explosion occurred with the Rowland Street main was 

 absolutely impervious to gas, then the explosion may 

 almost be regarded as proving the permeability of the 

 material of gas mains to mixtures of air and coal-gas. 



The practical lesson of the explosions is that some 

 means of certainly determining whether a gas main does 

 or does not contain gas must be found at once, and that 

 this means must not be the application of a light to an 

 opening in the main. The foreman who applied the fatal 

 match said that the pressure gauge showed the absence 

 of gas in the main ; but as the main contained a ciuantity 

 of gaseous mixture at rest, and not flowing through the 

 pipe, the gauge could not be expected to indicate the 

 presence of this mixture. 



It is almost amusing to read of the simple astonishment 

 of the two foremen when the fact was announced to them 

 that mixtures of coal-gas and air are explosive : twenty 

 or twenty-five years' experience in gas-works had failed 

 to teach them this fact. Yet the lives of the inhabitants 

 in the neighbourhood of Tottenham Court Road were 

 practically in these men's hands for the last three or four 

 months. 



With regard to the Risca disaster, of a different and 

 unhappily more fatal kind than the former, clouds of 

 smoke are said to have accompanied the explosion which 

 devastated the pits soon after midnight on Thursday last 

 (15th inst.), and we have it from the lips of a credible eye- 

 witness that fused and coked coal-dust is found adhering 

 to the timbers in those parts of the workings which have 

 been already visited, though not so conspicuous as in 

 some cases. In these respects therefore the recent ex- 

 plosion is only a repetition of similar events which have 



