2 24 



NA TURE 



IJuly 23, 1874 



nection between the two phenomena probable. I have observed 

 myself an extremely curious case in this respect on April 18, 1S42; 

 at 9. lo A. Ji., I saw by chance that the needle of the declination 

 instrument received a sudden jerk so that the scale was pushed 

 out of the field of view of the telescope. The oscillations 

 continued for some time ; at last the ordinary tranquillity was 

 restored. After some days I received the news from CoUa, 

 in Parma, that he had observed violent oscillations of the needle, 

 and comparisons showed that the movement had begun at the 

 same moment in Parma as in Munich. A short time after, the 

 rejiort of a French engineer was published, on a violent earthquake 

 which lie had observed in Greece ; and now it was found that 

 the earthquake had taken place in the same minute in which the 

 oscillations of the needle had been observed in Parma and 

 Munich. This, together with the many cases collected by Kreil 

 and Colla, leaves scarcely any doulit as to the presence of a close 

 connection ; but it is undecided whether one phenomenon is the 

 consequence of the other, or whether they botli come from the 

 same source. The same connection between earthquakes and 

 magnetic disturbances was observed by Lamont at the earth- 

 quake which took place in Greece in December 1S61. He 

 communicates his observations \.QPoggemiorffs Aumilcn (vol. cxv. 

 I 76) in the following words : " As the connection of the magne- 

 tism of the earth with earthquakes still belongs to the insuffi- 

 ciently ascertained relatives, it will not appear irrelevant if I 

 communicate a fact bearing upon this question. On December 

 26, 1S61, at 8 o'clock A.M., when I took down the position of 

 the magnetical instruments (some of whicli are put up in the 

 magnetical observatory, viz. two for declination, two for in- 

 tensity, and two for dip), I observed in all the instruments an un- 

 common restlessness, consisting in a quick and irregular decrease 

 and increase in the declination, and at the same time a trembling 

 in the vertical direction. The trembling of the needle only lasted 

 for a short time, but tire quick changes lasted until 8,30 o'clock 

 with gradually increasing violence. Some days later the news 

 was received of an earthquake which, exactly coincident with tlie 

 above observations, had caused great destruction in many parts 

 of Greece." (Philosophical Magazine, June 1S72.) This goes 

 far to show that terrestrial magnetism it to be correlated with the 

 lorce which is shrinking the earth. Henry H. Howorth 



COLLIERY EXPLOSIONS 



IT is astonishing that, notwithstanding the many gene- 

 rations during which coal-nrining has been carried on 

 in this country, so comparatively little has been done 

 to investigate scientifically the causes of explosions in 

 coal-:nines, and thereby discover an antidote to a con- 

 stantly recurring danger, one which adds considerably to 

 the yearly bills of mortality, and still more to the number 

 of widows and orphans. No doubt a considerable propor- 

 tion of these sad accidents is owing to the carelessness 

 of miners themselves, but very many are, without doubt, 

 also due to ignorance, on the part of all concerned, of the 

 conditions under which coal-mining must be carried on. 

 Only the other day a melancholy tale of death and wide- 

 spread mourning comes from Wigan — fifteen men killed, 

 leaving behind them at least thirty-one persons destitute 

 of the means of gaining a livelihood. We are afraid that 

 the frequency of such accidents has made the public 

 somewhat callous in the matter ; but a little consideration 

 must show the vast importance of acquiring a thorough 

 knowledge of the conditions under which they may 

 happen. To this end the pa; cr recently read before the 

 Royal Society by Mr. William Galloway, Inspector of 

 Mines, is an important contribution ; and we hope that 

 the author and others who are competent will continue 

 their investigations until, if explosions cannot be pre- 

 vented, they may at least be foreseen and provided 

 against. 



The opinions promulgated by Sir Humphry Davy and 

 the eminent Colliery Viewers who were his contempo- 

 raries, regarding the security afforded by the use of the 

 safety-lamp, have been accepted with hesitation by mnny 

 of their successors during the last twenty or thirty years ; 

 and this is not to be wondered at when we consider the 



large number of disastrous explosions by which thousands 

 of lives have been lost in mines in which these lamps 

 were in constant use. The illustrious in^ cntor himself 

 had discoveied and pointed out, that if the lamp were 

 exposed to the action of an explosive current, the flame 

 might pass through the meshes of the wire-gauze and so 

 originate an explosion ; but when in good order it was 

 considered to be safe under all other circumstances, until 

 the experiments were ttiade which form the subject of Mr. 

 Galloway's paper. 



At first, and for many years after the introduction of 

 the safety-lamp, the cause of nearly every explosion was 

 attributed to carelessness on the part of the workmen 

 using it ; then it was observed that a quantity of fire- 

 damp, suflicient to render some of the air-ci!rrents explo- 

 sive, was sometimes suddenly given off by the strata, and 

 these " outbursts of gas," as they are called, were assumed, 

 in tlie absence of any other explanation, to have caused 

 many explosions. On Dec. 12, 1866, however, the 

 great explosion took place at the Oaks Colliery ; as it was 

 known to have happened simultaneously with the firing 

 of a heavily-charged shot in pure air attention was drawn 

 to the coincidence ; and it appears that some search has 

 usually been made for evidence of recent shot-firing in 

 mines in which explosions have occurred since that date. 

 Accordingly we find from the reports of the Inspectors of 

 Mines that shot-firing was carried on in seventeen out of 

 twenty-two collieries, at which important explosions have 

 happened since Dec. 12, 1866; safety-lamps were cer- 

 tainly used in twelve of these collieries, and probably 

 in the whole seventeen ; in eight cases it was ascertained 

 that a shot had blown out the tamping at or about the 

 time of the explosion ; in two an empty shot-hole was 

 found from which it was supposed the tamping had been 

 blown ; in three a shot had been fired, bringing down 

 the coal or rock ; lastly, there were five collieries at which 

 two or more explosions took place simultaneously, in 

 ditferent parts of the mine unconnected by a train of 

 explosive gas. The Scaham explosion was a remarkable 

 one ; a heavily charged shot was fired in pure air in one 

 of the in-take air-courses, and, according to the statement 

 of three men who survived, the explosion of firedamp fol- 

 lowed the shot immediately. 



Two methods of accounting for the simultaneousness 

 of the explosion of firedamp with the firing of the shot 

 have been suggested in the reports of the Inspectors 

 of Mines : one of them supposes that the firedamp has 

 been ignited directly by the shot ; the other that the 

 concussion of the air cauied by the explosion of gun- 

 powder dislodges gas from cavities in the roof and from 

 grooves, and that this gas passing along in the air-cur- 

 rents is ignited at the lamps of the workmen. In some 

 instances when it has been known to be highly improba- 

 ble that any gas existed nearer to the shot-hole than 10, 

 20, or even 40 ft., the advocates of the former hypothesis 

 have taken it for granted that the gases issuing from the 

 shot-hole were projected through the air as far as the 

 accumulation of firedamp, retaining a sufficiently high 

 temperature to ignite it on their arrival. On the other 

 hand the advocates of the latter hypothesis have not 

 attempted to show how the gas, which they assumed could 

 be dislodged in quantity by a sound-wave and its reflec- 

 tions, could be ignited in those cases in which safety- 

 lamps only were used. It is no doubt highly probable, 

 however, that when once an explosion of firedamp has 

 been initiated in one way or another, and large bodies of 

 air are driven through the passages of a mine with great 

 velocity, explosive accumulations will be dislodged from 

 cavities and grooves and pressed through the safety-lamps 

 with the velocity requisite to pass the flame. 



In the beginning of the year 1S72 Mr. Galloway first 

 thought it probable that a sound-wave originated by a 

 blown-out shot, in passing through a safety-lamp burning 

 in an explosive mixture, would carry the flame through 



