82 On Recent Progress in the History of 
firm: rolls of an explosive material are obtained, which 
burns with considerable violence in open air, and the pro- 
pelling effect of which, in small arms, has occasionally been 
found greater than that of a corresponding charge of rifle 
powder. Moreover, the material, if submitted in small por- 
tions to violent percussion, exhibits but little tendency to 
detonation. Butas no reliance can be placed ona sufficient 
uniformity of action in a firearm, of these explosive rolls, 
this alone sufficed to prevent their competing with powder. 
The same description of explosive preparation, differing from 
that of M. Hochstadter ina trifling modification of its com- 
position, which is certainly not likely to lead to its greater 
success, has recently been brought forward in this country 
by M. Reichen and Mr. Melland. 
One or two other much cruder explosive preparations, 
containing chlorate of potash, alone or in conjunction with 
saltpetre, have met with some application to blasting pur- 
poses. One of these consisted of spent tan, in small frag- 
ments, which was saturated with the oxidizing agent, and 
afterwards dusted over with sulphur. When flame or a 
red-hot iron is applied to this preparation, it deflagrates 
very slowly and imperfectly ; but when employed in blast 
holes, where it is confined within a small space, it develops 
sufficient explosive force to do good work. In addition to 
comparative cheapness, the great advantage of safety was 
claimed for this material by its inventor, a claim which was 
substantiated by the partial destruction by fire, on two 
occasions, of a manufactory of thesubstance near Plymouth, 
without the occurrence of an explosion. 
The accidental explosions of gunpowder which are occa- 
sionally heard of, occur, in most instances, at the manufac- 
tories, and in the course of some operations (especially that 
of incorporation) to which the explosive mixture is com- 
_ mitted. The only means of guarding against, or reducing 
as much as possible, the liability to the occurrence of these 
accidents, consist in the strictest attention to the precau- 
tionary measures and regulations which experience has 
proved to be essential to safety, and which, in spite of the 
strictest supervision, are unquestionably sometimes over- 
looked or imperfectly carried out by workmen. Explosions 
of gunpowder, generally of a serious character, do occur, 
however, though very rarely, during the transport of the 
material, or in the magazines where it isstored. The great 
explosion of a gunpowder magazine at Erith, in September, 
1864, specially directed the attention of Government and 
