101 Mr. F. A. Abel [April 28, 



generally considerable, bnt it appears that exaggerated estimates are 

 entertained of the distance to which, in the absence of dust, the flame 

 will be projected, and it is probable that the large volumes of flame, 

 extending occasionally to many yards from the spot where the shot 

 was fired, are in a great measure due to the ignition of dust raised by 

 the concussion and rush of air at the instant of firins. Xr. Hall, in 

 his experiment* in the adit, found that the flame from the shot of 

 4 lb. of powder reached to a distance of only 18 to 21 feet when 

 no dust was present. A few months ago that official directed the 

 attention of the lecturer to the occurrence of two accidents in the 

 Liverpool district, each one occasioned by a shot of 1 lb. of powder 

 blowing out its stemmingj without shaking or bringing down any 

 coal. In both instances the shot lighter and two pitmen had retired 

 about 100 feet from the seat of the shot, that is. about 30 feet in a 

 straight line with it, and 60 to 80 feet along both directions of a 

 working running at right angles to the drift in the face of which the 

 charge was fired. In the case of one accident, a man was killed, 

 and serious injuries were sustained by the other men in both 

 instances. There were signs of charring upon the props up to, 

 and 5 or 6 feet beyond, where the men were standing, but they 

 did not extend farther. The drift and the level in which these 

 accidents occurred were 5 feet high and 12 fc^t wide. Mi'. Hall 

 informed the lecturer that a strong impression existed among 

 mining men on the spot that the flame of the shot, quite unaided 

 by gas or coal-dust (the latter was known to be present), would 

 have extended so as to produce the effects described. This appeared 

 so at variance with Mr. Hall's experiments in an underground 

 working, and with Mr. Abel's own experience in other directions, 

 that the latter has endeavoured to obtain some precise experi- 

 mental data with regard to the distance to which anv burning 

 effect from a blown-out charge of 1 lb. or IJ lb. of powder would 

 extend in a mine-working, in the absence of dust. "With this object 

 he availed himseK of the friendly assistance of Major Durnford, 

 E.E., Instructor in Field Fortifications at the School of Military 

 Fjigineering, Chatham, under whose direction Lieutenant Eaban has 

 carried out an instructive series of experiments in accordance with 

 suggestions made by Mi*. Abel as the work proceeded. 



The locality selected for the first experiments formed a portion of 

 some obsolete fortifications at Chatham, and consisted of a masonry 

 gallery or Caponier, 8 feet 8 inches high to the spring of the arch, and 

 8 feet wide below the arch, to a distance of 28 feet from the closed 

 end ; from that point it tapered on one side to 6 feet along a length of 

 2 feet 6 inches, and was 6 feet wide for a length of 3 feet 6 inches, 

 np to a pier or square column 4 feet by 3 feet 6 inches ; round which 

 the gallery curved, being at this part 4 feet 2 inches wide. The 

 straight part of the gallery, from the dead wall at one end to the 

 projecting pier at the other, was 31 feet long. In the wall to the 

 left of the blocked end there were six narrow loop-holes up to the 



