SCIENCE AND INDUSTRY. 
between two French men-of-war that were lying parallel to one another, 
and fired simultaneously both his broadsides at them, and then sailed 
away, leaving each to blow the other out of the water in the belief that 
it was firing at the adversary that had dared to attack it. The clouds of | 
smoke prevented either discovering its mistake. 
But in the new powder nothing is left unconsumed. The whole is 
turned into invisible gas. Aiming, therefore, continues possible; indeed, 
each shot is a sighting shot for the next. This makes it imperative 
that the position of guns should not be altered by firing, in order that 
they may correct their aim by past results; and they are therefore 
mounted in cradles with arrangements to take up the recoil, and return 
the gun to its original position after firing. Quick-firing and machine- 
guns can be used with accuracy, and their use is now the fundamental 
consideration in much of our military tactics. It would be hard to 
exaggerate the extent to which military science had been changed by 
this invention of smokeless powder. 
Bic Berrua ExpLarNep. 
But science has not completed its service to war in respect of explo- 
sives when it had thus endowed it with a perfect propellent. There 
remain the high explosives with their tremendous pressure. Recent 
measurements of pressures produced instantaneously by high explosives 
point to a figure of 300 tons per square inch. But this inadequately 
expresses the contrast between them and those others of which he had 
been speaking. It took no notice of the rate at which the pressure rose. 
The rate at which that pressure comes on in a 6-in. gun has been found 
to be about 10,000 tons per second, so that it rises to the full pressure 
of 15 to 20 tons in something under the five-hundredth part of a second. 
In a rifle, the rate of rise is perhaps ten times as great, but the period is 
proportionately shorter. In a good high explosive, the rate of rise per 
second was several millions of tons per square inch, and the period was 
a fraction of a thousandth part of a second. Hence the shattering 
effect of these high explosives. 
Such violence of explosive force is just what is needed for shells, 
provided that the explosives are not too sensitive, or, in other words, 
that they stand the shock of the discharge of the gun without exploding. 
But here a strange peculiarity shows itself. They have two ways of 
exploding. The one gives a comparatively mild explosion, comparable, 
say, with that of gunpowder; the other, a fierce detonation, the violence 
of which is akin to that of guncotton. No one has penetrated the 
mystery of this. It undoubtedly depends on the initial disturbance 
which sets the explosive off. If that is of a sufficiently intense type, and 
is rightly communicated to the mass of the explosive, it produces detona- 
tion, and the shell is rent to pieces. If not, we have only an explosion 
which opens out the shell, but does little more. It needed much research 
to give us practical control of high explosives in this respect. In the 
Boer War we used lyddite in our shells—a high explosive of the finest 
quality; but we did not know how to detonate it with certainty, and in 
only one type of gun was it of use. By the commencement of the present 
war we had, however, learnt how to detonate with fair, but not absolute, 
certainty the high explosives then used in the service. But soon 
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