86 ANNUAL OF SCIENTIFIC DISCOVERY. 



SOME OF THE CAUSES, EFFECTS, AND MILITARY APPLICATIONS 



OF EXPLOSIONS. 



The following is a report of a lecture on the above subject recently 

 delivered before the Royal Institution, London, by Mr. Abel, director 

 of the chemical establishment of the British War Department. 



The phenomena which we are in the habit of classing under the 

 term explosions are all due, I need scarcely say, to a sudden and 

 considerable expansion of matter. The successful effort, for exam- 

 ple, of confined particles of air to escape from the bonds within 

 which they have been compressed, and to re-assmne the position 

 which they originally occupied relatively to one another, is always 

 accompanied by the production of sound, the violence of which is 

 regulated by the extent and suddenness of the expansion and the 

 amount of resistance to be overcome, and, consequently, by the vio- 

 lence with which the particles of air dash against and impart vibra- 

 tion to the surrounding atmosphere, or other particles of matter with 

 which they come into collision ; as is the case when I compress air with- 

 in this bladder, until a point is reached at which the cohesive force, 

 holding the particles of the bladder together, is overcome by the pres- 

 sure exerted from within, and we have a sound produced. [This was 

 illustrated by air's being forced by a syringe into a small India-rubber 

 balloon until the pellicle burst with a slight report.] What we call 

 explosions may also be produced by a sudden or very rapid conver- 

 sion of solid or liquid into a gas or vapor, by the sudden change of 

 state (as we commonly call it) of matter, brought about by the action 

 of heat, which is therefore one great in fact the most important 

 source of explosions. 



As it is, however, impossible to treat the whole subject of explo- 

 sions in one lecture, I therefore confine myself to the consideration 

 of those explosions which are brought about directly or indirectly by 

 chemical agency. 



When chemical action produces, or is followed by, an explosion, 

 we know that the main cause of that explosive effect or result, of 

 which I have just endeavored to point out the general nature, is the 

 development of heat consequent upon the disappearance of chem- 

 ical activity ; and we also know that the amount of heat if I may 

 use this term in speaking of such an agency of heat corresponds to 

 the energy of the chemical action ; just in proportion, therefore, as 

 W T C have chemical energy exhibited, we have heat developed. There 

 is another cause to which we may refer the production of explosions,, 

 and that is the alteration in the state of matter resulting simply from 

 chemical change. Solids may, as you all know, be, under these cir- 

 cumstances, converted into vapors or gases; such changes may be 

 effected very suddenly, and quite independently of any heat devel- 

 oped ; and the sudden expansion thus brought about would naturally 

 produce the effect of an explosion. We may readily conceive that, 

 if a small quantity of powder, such as the charge used in a small-arm 

 or rifle (weighing about seventy-five grains), were suddenly converted, 

 independently of the action of heat, into a considerable volume of 

 gas, an explosive effect would be produced. But, accompanying 

 this change of state, we have, in the actual case of the explosion, 



