It was, however, nothing but a trap, for it had no exit. As soon as a number of the assailants had poured into this trap, their exit was suddenly cut off by machinery provided for the purpose, and at the same time a quantity of sulphur and lighted charcoal was shot into the gallery from above, and the aperture instantly closed. It would be absolutely impossible that any one who had been enclosed in that terrible chamber should escape with life, for the first breath of that deadly vapour would render the strongest man insensible. * * * * * NATURE, as usual, has anticipated Art even in this particular. In several parts of England, and especially along the shores of the Thames towards Gravesend, a little beetle is to be found under the flat stones of the river bank. Its scientific name is _Brachinus crepitans_. When this insect is alarmed, it has the power of ejecting a peculiar liquid, which, when it comes in contact with the atmosphere, bursts into a sort of pale blue-green flame, followed by a kind of smoke. Sometimes, when a tolerably large stone is lifted, the little explosions will go popping about in a most curious manner. Indeed, they carry reminiscences of school days, when it was a joy to distribute single grains of coarse gunpowder on the bars of the grate, and watch them melt, take fire, explode, and send forth little clouds of smoke. The insect is popularly called the Bombardier-beetle. Whether or not this capability be given as a means of defence I cannot say, but it assuredly answers that purpose. There are several of the voracious Carabidæ, or Ground-beetles, which would be very glad to make a meal of the Brachinus. When, however, the Bombardier-beetle finds itself on the point of being overtaken, it elevates the abdomen with a peculiar gesture, and ejects the liquid. The effect on the pursuer is remarkable. It seems overwhelmed and stupefied by the sudden attack, moves about for awhile as if blinded, and, by the time that it has recovered its sense, the Bombardier-beetle is out of sight. In some of the hotter parts of the world there are several species of Bombardier-beetles which attain considerable size, and their discharge is powerful enough to discolour the skin of the human hand. * * * * * I HAVE felt some little difficulty in classifying the curious invention which will now be described, but, as it is used for the purpose of making bullets, I have placed it in the category of War. [Illustration: SILK APPARATUS OF SILKWORM.] [Illustration: BULLET-MAKING APPARATUS.]