THE DEBT TO SCIENCE. 
the combustible and the oxygen are present in one and the same molecule. 
Like the lion and the lamb of which the prophet speaks, they lie down 
together, and it is not until the molecule is shattered by heat or shock 
or some other like agency that they rush together into combustion. As 
might be expected, such a combustion is instantaneous, and the explosion 
it produced is very violent, far exceeding all that had previously been 
known. These bodies were the earliest forms of what are now known 
as high explosives. 
A Great Discovery. 
Such a discovery was sure to be seized upon for the use of war, but 
its employment was delayed from the very magnitude of its suecess— 
the explosions were too violent. These explosives could not be used in 
guns, because they would burst the gun; nor in shells, because even if 
they would stand the shock of firing, they would shatter the shell into 
too small fragments to be effective. So the use of these early high 
explosives in war, except for blasting or like destructive purposes, made 
little advance for many years, until it was discovered that by dissolving 
them in some volatile solvent, and subsequently driving it off, there was 
left a substance resembling gelatine which could be cut into pieces of 
any desired shape or size. It possessed all the power of the original 
explosive, but its rate of burning was wholly different. You will under- - 
stand the reason of this when I say that though it was a true explosive, 
burning with extreme rapidity, it was a poor conductor of heat. When 
the charge was fired, all the pieces commenced to burn on the surface, 
and the combustion was so rapid that it spread itself through each piece 
of the material more quickly than the high temperature could arrive 
at the centre of that piece by conduction of heat. Hence it followed 
that the pieces always burn from the outside inwards, and the explosion 
never commences inside the piecé, so that by changing the shape and 
size of the pieces into which the material was cut, and thus making the 
amount of their surface large or small compared with their bulk, you 
can make a powder which would burn more or less quickly. For 
instance, a favourite method of increasing the rapidity of burning is 
by perforating the pieces so as to increase the surface without increasing 
the bulk. In this way, there could be made out of the same substance 
powders suitable for small arms which required a very rapidly-burning 
powder, and for large guns which required a comparatively slowly- 
- burning powder. You must understand that I am using the words quick 
and slow in a comparative sense only. The actual time required is 
always small. In the biggest gun loaded with the coarsest powder, the 
time of the burning of the charge would be something of the nature of 
one twenty-fifth of a second. 
But the quality which caused the discovery of these gelatinized 
powders to revolutionize tactics, both by land and sea, was that they 
were smokeless. In gunpowder there is much that takes no part in the 
combustion and is expelled as fine dust. It is this which causes the 
smoke which always accompanies the use of gunpowder, and which not 
only fouls the gun, but made.aiming an impossibility after the first 
volley in continuous firing. The great feature of Admiral de Saun- 
marez, the local hero of Guernsey, was that he drove his frigate by night 
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