Sept. 1, 1864.] THE TECHNOLOGIST. 



USES OF GUN-COTTON. 51 



When there is no smoke, as with gun-cotton, the aim of every gun may- 

 be precise and deliberate. The diminished heat between decks will 

 also tell powerfully in favour of gun-cotton. In our armour-plated 

 ships also there is more value in breech-loading guns than in any other 

 use of artillery. It is one of the necessities of breech-loading mecha- 

 nism that it be kept clean, and nothing tends more to derange its 

 perfect action than the great heat which gunpowder imparts to the 

 gun from which it is fired. 



That gun-cotton has the convenience of not heating the gun has been 

 thus proved. One hundred rounds were fired in thirty-four minutes with 

 gun-cotton, and the temperature of the gun was raised 90 degrees. One 

 hundred rounds were fired with gunpowder, and triple the time allowed 

 to cool the gun, which, nevertheless, was heated so much as to evaporate 

 water with a hissing sound, which indicated that its temperature was 

 much above 212 degrees. Under these circumstances the firing with 

 gunpowder had to be stopped, while that with gun-cotton was comfortably 

 continued to 180 rounds. 



It is also a matter of practical convenience that gun-cotton, insomuch 

 as it is lighter, can be carried more easily and farther than gunpowder ; 

 and it may be wetted without danger, so that when dried in the open 

 air, it is as good for use as before. 



III. We have now to ask — Is it cheaper ? The answer to this ques- 

 tion must be qualified — pound for pound, it is dearer ; we must, there- 

 fore, judge of its cheapness by its effect, not by weight merely. But 

 where it does six times as much work, it can then be used at six times 

 the price per pound, and still be as cheap as gunpowder. As far as we 

 yet know, the prices of gun-cotton and gunpowder are nearly equal, 

 and it is only therefore where the one has advantages and conveniences 

 beyond the other, and is more especially suited for some specific purpose, 

 that it will have the preference. Effective cheapness 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 oper 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 lbs. 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 lbs. had been taken 



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