76 HYDROGENIUM ; THE RELATION OF HYDROGEN TO PALLADIUM. 
that substance ; it is now demonstrated that gun-cotton and other explosive compounds 
and mixtures do not necessarily require confinement for the full development of their 
explosive force, but that this result is attainable (and very readily in some instances, 
especially in the case of gun-cotton) by means similar to those applied in the case of 
nitro-glycerine. 
The manner in which a detonation operates in determining the violent explosion of 
gun-cotton, nitro-glycerine, etc., has been made the subject of careful investigation. It 
is demonstrated experimentally that the result cannot be ascribed to the direct operation 
of the heat developed by the chemical changes of the charge of detonating material 
used as the exploding agent. An experimental comparison of the mechanical force ex¬ 
erted by different explosive compounds, and by the same compound employed in differ¬ 
ent ways, has shown that the remarkable power possessed by the explosion of small 
quantities of certain bodies (the mercuric and silver-fulminates) to accomplish the deto¬ 
nation of gun-cotton, while comparatively very large quantities of other highly explo¬ 
sive agents are incapable of producing that result, is generally accounted for satisfac¬ 
torily by the difference in the amount of force suddenly brought to bear in the different 
instances upon some portion of the mass operated upon. Most generally, therefore, the 
degree of facility with which the detonation of a substance will develope similar change 
in a neighbouring explosive substance may be regarded as proportionate to the amount 
of force developed within the shortest period of time by that detonation, the latter being, 
in fact, analogous in its operation to that of a blow from a hammer, or of the impact of 
a projectile. 
Several remarkable results of an exceptional character have been obtained, which in¬ 
dicate that the development of explosive force under the circumstances referred to is not 
always simply ascribable to the sudden operation of mechanical force. These were es¬ 
pecially observed in the course of a comparison of the conditions essential to the deto¬ 
nation of gun-cotton and of nitro-glycerine by means of particular explosive agents 
(chloride of nitrogen, etc.), as well as in an examination into the effects produced upon 
each other by the detonation of those two substances. 
The explanation offered of these exceptional results is to the effect that the vibrations 
attendant upon a particular explosion, if synchronous with those which would result 
from the explosion of a neighbouring substance in a state of high chemical tension will, 
by their tendency to develope those vibrations, either determine the explosion of that 
substance, or at any rate greatly aid the disturbing effect of mechanical force suddenly 
applied, while, in the instance of another explosion, which developes vibratory impulses 
of different character, the mechanical force applied through its agency has to operate 
with little or no aid, greater force, or a more powerful detonation, being therefore re¬ 
quired in the latter instance to accomplish the same result. 
Instances of the apparently simultaneous explosion of numerous distinct and even 
somewhat widely separated masses of explosive substances (such as simultaneous ex¬ 
plosions in several distinct buildings at powder-mills) do not unfrequently occur, in 
which the generation of a disruptive impulse by the first or initiative explosion, which 
is communicated with extreme rapidity to contiguous masses of the same nature, appears 
much more likely to be the operating cause, than that such simultaneous explosions 
should be brought about by the direct operation of heat and mechanical force. 
A practical examination has been instituted into the influence which the explosion of 
gun-cotton through the agency of a detonation, exercises upon the nature of its meta¬ 
morphosis, upon the character and effects of its explosion, and upon the uses to which 
gun-cotton is susceptible of application .—Proceedings of the Royal Society. 
HYDROGENIUM; THE RELATION OF HYDROGEN TO PALLADIUM. 
(Continued from page 649, Vol. AT.) 
It has often been maintained on chemical grounds that hydrogen gas is the vapour of 
a highly volatile metal. The idea forces itself upon the mind that palladium with its 
occluded hydrogen is simply an alloy of this volatile metal, in which the volatility of 
the one element is restrained by its union with the other, and which owes its metallic 
