1876.] 



of Coal-dust in Colliery Explosions, 



365 



ments were begun at 11 A.M., and concluded at 6 p.m. The meteoro- 

 logical observations inside the cabin at 3.15 p.m. were : — temp. 57° Fahr. ; 

 humidity 79 ; bar. 30*15. The same water was employed in all the 

 experiments ; and it may be safely assumed that the humidity of the 

 mixtures of firedamp and air was 100. 



The following phenomena were observed in connexion with the differ- 

 ent mixtures : — 



1 firedamp to 14 air — slightly explosive. 



1 to 15 — inflammable : the flame of the mixture would not pass down 

 through the hole in the tin-plate cover of the chimney ; but when the 

 small flame, employed to ignite it, w T as put through the hole to a depth of 

 | inch or so below the tin-plate cover, the mixture ignited, and a hori- 

 zontal, waving sheet of blue flame, occupying the w r hole sectional area of 

 the chimney, passed down through it in about two or three seconds, and 

 was extinguished on reaching the bottom. 



1 to 16 gave a voluminous, waving, spiu die-shaped, pale blue cap 3| 

 inches high. 



Fig. 8 represents the forms and sectional dimensions of the various " caps," from 

 sketches and measurements taken at the time they were observed. 



