1900.] on Some Modern Explosives. 331 



small arms ; and here are successive sizes, adapted to successive larger 

 calibres, imtil we reach this size, which is that employed for the 

 charge of the 12-inch 50-ton guns. 



A couple of the smaller cords I burn, both for purposes of com- 

 parison and to draw your attention to the entire absence of smoke. 



The smoke of the gunpowder you see still floating near the ceiling ; 

 but little or no trace of smoke can be seen from such explosives as 

 guncotton, cordite or ballistite, their products of combustion being 

 entirely gaseous. 



You will have observed that in the combustion which you have just 

 seen there is no smoke, but I must explain, and I shall shortly show 

 you, that this combustion is not quite the same as that which takes 

 place, for instance, in the chamber of a gun. Here the carbonic oxide 

 and hydrogen, which are products of explosion, burn in the air, giving 

 rise, with the aid of a little free carbon, to the bright flame you see, 

 and somewhat increasing the rate of combustion. In a gun, however, 

 owing chiefly to pressure, the cordite is consumed in a very small 

 portion of a second. 



In order to illustrate the effect of pressure upon the rate of com- 

 bustion, I venture to show you a very beautiful experiment devised 

 by Sir F. Abel. It has been shown in this room before, but it will 

 bear repetition. 



In this globe there is a length of cordite. I pass a current through 

 the platinum wire on which it is resting, and you see the cordite burns. 

 I now exhaust the air and repeat the experiment. The wire is red- 

 hot, but the cordite will not burn. That the failure to burn is not 

 due to the absence of oxygen is shown by plunging lighted cordite 

 into a jar of carbonic acid, where, although a match is instantly put 

 out, the cordite continues to burn — but observe the difference. There 

 is no longer any bright flame, although the cordite is being consumed 

 at about the same rate as when burned in air ; and when a sufficient 

 quantity of the C0 2 is displaced, I can make the inflammable gases 

 iguite and burn at the mouth of the jar. 



Another illustration is also instructive. I have here a stick of 

 cordite wrapped round with filter paper ; I dip it in water and light 

 the end. You may note that at first you see the bright flame ; but, as 

 the combustion retreats under the wet filter paper, there appears a 

 space between the flame and the cordite, the flame finally disappears, 

 hot gases with sparks of carbon alone showing. 



One other pretty experiment I show. I have here a stick of cor- 

 dite, which I light. When fairly lighted I plunge it in this beaker 

 of water. The experiment does not always succeed at the first 

 attempt, but you now see the cordite burning under the water much 

 as it did in the jar of carbonic acid. The red fumes you observe are 

 due to the formation of nitric peroxide, caused by the decomposi- 

 tion of the water by the heat. 



I have on the table samples of certain other smokeless explosives 

 of the same class. Here is a ballistite used in Italy. Here is some 



z 2 



