450 THOUGHTS ON THE 



way of determining, they jump at once to the necessary 

 consequence of the dilatation of a body, and do not accu 

 rately consider what comes first in the order of nature. 

 For that the substance of the gunpowder, after having been 

 converted into flame, must occupy a larger space, is doubt 

 less a thing of necessity ; but that the substance of the gun 

 powder should be inflamed at all, and that so instan 

 taneously, is not determined by a like necessity, but depends 

 on an antagonism, and comparative force of motions. For 

 there is not a doubt, that the compact and heavy body 

 which is expelled or dislodged by this motion, offers consi 

 derable resistance before it gives way, and, if it happen to 

 be the stronger, is victorious ; that is to say, the flame, in 

 that case, does not cast out the ball, but the ball stifles the 

 flame. If, therefore, instead of gunpowder, you take sul 

 phur, asphaltum, or the like, bodies which are also quickly 

 inflammable, and (as the closeness of particles in bodies 

 hinders ignition) reduce them to a grain like gunpowder, 

 mixing up with it a small quantity of the ashes of the 

 juniper, or some other very combustible wood; yet should 

 the nitre be wanting, that rapid and powerful motion does 

 not follow : the motion to perfect inflammation is impeded 

 and fettered by the resisting body, so that it cannot fully 

 expand and take effect. For besides the motion of inflam 

 mation, which chiefly arises from the sulphureous part of 

 the gunpowder, there is yet another powerful and violent 

 motion in the case. This is caused by the crude watery 

 ether, which is extricated from the nitre in part, but chiefly 

 from the charcoal, and which not only itself dilates, as ex 

 haled essences are wont to do, on the application of heat, 

 but at the same time (which is the principal circumstance) by 

 a motion of extreme rapidity, flies off and breaks forth from 

 the heat and flame, thus distending and opening passages 

 for the inflammation to follow. Of this motion we see the 

 simplest form in the crackling of the dry leaves of laurel or 

 ivy, when we cast them into the fire, and still more in salt, 

 which approximates more nearly to the substance under 

 examination. We also often observe something like this in 

 the tallow of candles when melted, and in the windy rustle 

 of green wood set on fire. But it is chiefly discernible in 

 quicksilver, which is an extremely crude substance, not 

 unlike the water of a chalybeate spring ; and the force of 

 it, if tried by the application of fire, and prevented from 

 egress, not greatly inferior to that of gunpowder itself. 

 Men ought, therefore, to be admonished and conjured from 



