404 Original Articles. [July, 
veniences beyond the other, and is more especially suited for some 
specific purpose, that it will have the preference. Effective cheap- 
ness will therefore depend mainly on which of the two does best the 
particular kind of duty required of it. 
To illustrate how curiously these two powers, gun-cotton and gun- 
powder, differ in their nature, and how the action of gun-cotton may 
be changed by mechanical arrangements, we may take one kind of work 
that is required of both :—If a General want to blow open the gates of 
a city, he orders an enterprising party to steal up to the gate, with a 
bag containing 100 lbs. of gunpowder, which he nails to the gate, and 
by a proper match-line he fires the gunpowder and bursts open the 
gate. If he nailed a bag of gun-cotton of equal weight in the same 
place and fired it, the gun-cotton would fail, and the gate would be 
uninjured, although the 100 Ibs. of gun-cotton is sixfold more 
powerful than the gunpowder. Here, then, gunpowder -has the 
advantage—both weight and effect considered. 
But the fault here lies not in the gun-cotton, but the way of using 
it. If instead of 100 lbs. of gun-cotton in a bag, 25 Ibs. had been 
taken in a proper box made for this purpose, and simply laid down 
near the gate, and not even nailed to it, this 25 lbs. would shiver the 
gate into splinters. The bag which suits the powder happens not to 
suit the gun-cotton. 
Gun-cotton is therefore a power of a totally different nature from 
gunpowder, and requires complete study to know its nature and 
understand its use. It appears that both gunpowder and gun-cotton 
have special qualities, and may be peculiarly suited for peculiar uses. 
It is the duty of a wise people to make use of both to the ends they 
each suit best, without prejudice arising from the accident of novelty 
or antiquity. 
The nature of gun-cotton requires a double study, chemical and 
mechanical. It is not like steam, the same substance, whether in the 
form of ice or water or steam. It is one substance when as gun- 
cotton it enters the gun, and quite a different one when it has exploded 
and leaves the gun. Not only are the solids which enter converted 
into gas, but they form totally new combinations and substances. So 
that the marvellous changes which the chemist effects by the magic 
of his art take placein an instant of time, and during that almost 
inconceivably minute period of time, in a laboratory intensely heated, 
old substances are dissolved, their material atoms are redistributed, 
each atom released selects by natural affinity a new partner, these 
new unions are cemented, and at the end of this prolific instant totally 
new combinations of matter, forming what we call new substances, issue 
from the gun. It so happens that of these new substances, formed out 
of gun-cotton, all are pure transparent gases, while in the case of gun- 
powder there remain 68 per cent. of solid residue, and only 32 per 
cent. are pure gases. 
It is to chemistry however, that we must look for full and authen- 
tic information as to these wonderful changes: first, from the innocent, 
gentle cotton wool in which our wives and daughters wrap their jewels 
for soft keeping, into the terrible and irresistible compound of nitric 
