370 Mr. W. Galloway on the Influence [Mar. 2, 



for our papers on the Connexion between Colliery Explosions and "Weather, 

 it was remarked by both Mr. Scott and myself that several great explo- 

 sions had occurred in the years with which we had to deal (1868 to 1872 

 inclusive) during weather very similar to that which prevailed in the 

 beginning of December last. This phenomenon was more marked, how- 

 ever, on the last occasion than at any time during my own experience ; and 

 while I was investigating the causes of the Llan explosion the following 

 explanation presented itself to me, which I have now the honour of sub- 

 mitting to the consideration of the Fellows of this Society, with the 

 remark that this part of the subject will be more minutely investigated 

 by Mr. Scott and myself. 



If we assume that the magnitude of some colliery explosions has been 

 determined by the presence of coal-dust in the workings, and that the 

 hygrometric state of coal-dust changes with the humidity of the air with 

 which it is in contact, then it is an obvious conclusion that explosions of 

 this kind will be most likely to occur when the air in the mines is driest ; 

 for at such times not only will the coal-dust be most easily raised into 

 the air by the local explosion (which we may always suppose to happen 

 at any rate), but it will also be burned more easily than when it con- 

 tains a larger proportion of moisture. 



As an example we may take the case of a dry mine, in which the tem- 

 perature of the workings is 70° Fahr. During warm weather the air 

 which descends the shaft has a temperature of, say, 60° when it enters the 

 intake air-course ; at this stage it is also saturated with vapour, for there 

 is usually a little water trickling down the sides of a mine-shaft. The 

 temperature rises gradually as the current draws nearer to the faces, and 

 at length attains its maximum when the newly exposed face of the coal 

 has been passed. During this process the humidity has also been increas- 

 ing to some extent, always remaining below complete saturation, however, 

 in a mine of this kind. 



In very cold weather, on the other hand, the same current may some- 

 times have a temperature of 32°, or less, when it reaches the bottom of 

 the shaft ; and since it passes through the same workings, its tempera- 

 ture rises to 70° as before. It is plain, therefore, that, in the latter case, 

 the ventilating-current must either obtain an additional supply of mois- 

 ture from the workings (about \ pound for every 1000 cubic feet of air), 

 or it must be drier than in the former case at every point of its course. 



Prima facie, then, this process of reasoning leads us to the conclusion 

 that explosions whose magnitude is due to the influence of coal-dust will 

 happen most frequently during cold weather ; and, conversely, we might 

 expect to find that the magnitude of those explosions which occur during 

 cold weather is traceable, in some measure, to the influence of coal-dust. 



The data represented graphically in figures 9, 10, and 11 are closely 

 connected with this part of the subject : figs. 9 and 10 show the 

 variations of temperature in the cabins at the bottom of Ferndale and 



