SepL 8, 1887] 



NA TURE 



437 



The Svastika on English Walls.— The Solar Eclipse 

 of August 19. 



I GREATLY fear that practical builders will be uncourteous 

 enough to smile at Mrs. Murray-Aynsley's idea (Naturk, 

 August 18, p. 364) that the S-shaped iron bars seen on the walls 

 of houses are fire-emblems or survivals of sun-worship. They 

 are common enough in every county of England and elsewhere ; 

 in fact, wherever the scamping of jerry builders or the lapse of 

 time has caused walls to give way or bulge outwards. The bolt 

 in the centre is not merely to hang them up, but is the end of a 

 long and strong iron bar passing right through the building and 

 attached to a similar curved brace on the other side, or at any 

 rate fixed to some firm unyielding part of the masonry. The curved 

 shape is simply chosen as that which embraces and gives support 

 to the greatest area of brick or stone surface without the 

 necessity of having a solid, continuous plate. 



A propos of sun-worship, it is sad to reflect how much good a 

 little of it might have done in inducing that august but capricious 

 luminary to show himself to the thousands who looked in vain 

 for him on the morning of the recent eclipse. He seems to 

 have shone in splendour in longitudes east of the Urals, where 

 his worshippers abound, but to have hid himself in anger from 

 nearly the whole of unbelieving, scientific Europe. 



At Twer, between St. Petersburg and Moscow, where I was 

 myself, the early dawn was beautifully clear ; but first a dense 

 ground-mist enveloped us, and then, when enough wind sprang 

 up to clear this away and give us a glimpse of the sun about six- 

 tenths eclipsed, a heavy bank of rain clouds came up and put an 

 end to all hopes of observation. The commencement of totality 

 was pretty well marked by a sudden intense gloom, not, how- 

 ever, greater than (if even as great as) a London fog. 



At Berlin placards were extensively posted up a little later 

 in the day stating that "in con-equence of the unfavourable 

 weather the eclipse was postponed until the next day." This 

 might have been believed in France or Ireland, but it is harder 

 to take in the Teuton than the Celt. H. G. Madan. 



Eton College. 



Large Meteors. 



A PEAR-SHAPED fireball, rivalling Venus in brilliancy, passed 

 over Cardigan and Radnor in Wales on August 21 at llh. 2m, 

 It was observed by Mr. D. Booth at Leeds, and by the writer at 

 Bristol ; but the two paths, though likely to be very accurate as 

 regards the direction of flight, are somewhat discordant in the 

 beginning and end points. The radiant of the fireball was at 

 264" -f 61" in Draco, and agrees with the two following 

 showers : — 



1871 August 20-25 

 1887 August 14-23 



264 -^ 64 Tupman. 

 264 -f 62 Denning. 



The meteor referred to appears to have been observed at 

 Bristol much earlier in its track and when considerably higher in 

 the atmosphere than when noticed at Leeds. The mean of the 

 two places gives a height of 80 miles over a point 6 miles east of 

 Aberystwith to 45 miles above a place 7 miles west of Rhaya- 

 dergwy. The earth point was near Hay, Herefordshire. 



It would be important to hear if this fine meteor was observed 

 at any stations in the Midlands, in Wales, or on the south-east 

 coast of Ireland. As seen from Leeds it passed through Scutum 

 Sobieski, and at Bristol close to the star i Dracoiiis. 



Another fine meteor about equal to Venus wa^^ observed here 

 on August 30 at I4h. 25m. It left a bright streak in its path of 

 18" from 19" -\r 27" to 5° -1- 14°. Radiant at 46° -f- 43° near 

 )8 Persei. W. F. Denning. 



Bishopston, Bristol, August 31. 



Colliery Explosions and Atmospheric Pressure. 



There are few questions so much in need of a satisfactory 

 solution as the relationship which exists between colliery ex- 

 plosions and changes of atmospheric pressure. Before anything 

 was known of the weight, and variations in the weight, of the 

 air, before the barometer was discovered, miners had learned to 

 connect the state of their working-places with weather changes. 

 The old pits were very shallow, the workings very limited, and 

 the ventilation practically left to take care of itself, so that it is 

 not difficult for us to understand the effect of temperature rather 



than pressure on the atmosphere of the mine. " Trefoil damp," 

 "pease bloom damp," &c., sufficiently indicate the summer pre- 

 valence of the danger ; in winter "the damps were scarcely felt 

 or heard of." In the early part of the present century Mr. John 

 Buddie, the Newcastle viewer, having watched his barometer 

 and the mining reports became strongly of opinion that "acci- 

 dents from fire-damp always occur with a low barometer." 

 Faraday and Lyell's Report on the Haswell disaster of 1844 dwelt 

 upon the importance of officials taking into account the variations 

 of the barometer in the management of mines. Since then 

 numerous public Commissions and private inquirers, English and 

 foreign, have investigated the connexion supposed to exist be- 

 tween the exudation of gas and s. falling barometer. The earlier 

 decisions may be said to favour Mr. Buddie's opinion, but of late 

 years there appears to be a tendency to declare that the effect of 

 a low or falling barometer has been considerably over-rated — 

 that in reality it has little or no influence. Under whatever 

 conditions of pressure explosions formerly occurred, it is perfectly 

 clear from the experience of recent years that disasters take place, 

 as a rule, when there is an excess and not when there is a 

 deficiency of pressure. 



Mr. Dobson's Report to the British Association in 1855 

 showed from a large, though imperfect, number of observations 

 that up to the year 1854 accidents from fire-damp were most 

 frequent in the summer months June and July, the minimum at 

 the end of January ; the results being taken to prove indisputably 

 the general dependence of explosions upon the seasons of the 

 year. 



In the papers communicated to the Royal and to the Meteoro- 

 logical Societies between 1872 and 1874 by Messrs. Scott and 

 Galloway, it was however shown from 1369 accidents in twenty 

 consecutive years that the maximum occurred at the end of 

 January, the minimum in the middle of September. 



These very different results may be regarded as indicating the 

 great revolution which has taken place not only in the time at 

 which explosions occur, but also in the conditions of mining 

 operations. Pits are now of enormous depths, with most 

 extensive galleries, and the ventilating appliances are of the 

 most elaborate description. Possibly these changes have 

 modified very greatly the effect of weather variations. It must 

 be remembered that gas exists in mines under two quite distinct 

 conditions, that in the goaves and waste places being free and in 

 direct contact with the air, while the gas occluded in the solid 

 coal or imprisoned in faults is not in direct contact with the 

 atmosphere. In the former case it is generally agreed that the 

 accumulations of gas expand or contract with the changes of 

 atmospheric pressure. In the latter case we know that the gas 

 exists in the coal at a pressure of many atmospheres, so that it is 

 highly improbable that it is affected directly by the rise and fall 

 of the barometer. Indirectly, however, it would seem that a very 

 important effect results, but in direct opposition to the idea that 

 it escapes only with a falling barometer. 



Serious explosions are almost exclusively confined to deep 

 mines, where the management is perfect, and where every care 

 is taken to insure safety. Mystery surrounds each disaster, and 

 it is left to individuals to trace them to coal-dust, gas, or some 

 other favourite theory. Fortunately the illiterate manager has 

 given way to a different order of men, and from the interest 

 taken by mining engineers there is reason to believe that much 

 of the uncertainty which at present envelops the question will 

 be removed before long. Barometers are now common to all 

 mines, and they are studied with more or less interest by the 

 officials. For years past it has become clear to them that there 

 is no apparent connexion between the escape of gas and a falling 

 barometer : the firemen " in ordinary cases can forestall the 

 barometer by from twelve to twenty-four hours." This con- 

 clusion, based upon the ordinary observations of officials during 

 their daily routine of duty, has been confirmed by more precise 

 and carefully-planned systems of collecting information. 



Following the Seaham disaster of September 1880 (when the 

 centre of an anticyclone was over the northern counties), Mr. 

 Corbett arranged hourly observations, day and night, for several 

 months, showing the atmospheric pressure, the measurements of 

 gas which had escaped into the workings, and by means of 

 water-gauges the movements of the gas in parts of the workings 

 sealed from contact with the air. The water-gauges indicated 

 an out-bye pressure as much as 33, 35, 41, and 48 hours before 

 the barometers began to fall, while gas in measurable quantities 

 was to be found many hours before the mercury gave signs of 

 falling. On the Continent somewhat similar observations have 



