know the rats'-nests, and that he had seen them fired at, when many rats were killed, and fell out to the ground. He could tell me no more, and I think that, if original nests, as he held them to be, some grass must be woven in during their construction, as fir-spines have but little power of cohesion. The situation of these nests was worthy of notice, although there is scarcely a situation where a rat's-nest has not been found.—C. Horne, F. Z. S., in Science Gossip.
Spontaneous Explosions of Gun-cotton.—Fired in the open air, gun-cotton burns with great rapidity, but does not explode. It has accordingly been the practice to store the manufactured article in more or less open sheds, in boxes containing twenty-five or thirty pounds each. In this condition, however, several explosions have taken place; the most serious being one that occurred at Stowmarket, in England, something less than a year ago. In this case the ignition of the gun-cotton was shown to be due to the presence of a large quantity of sulphuric acid in the stored material; but why it should explode when ignited, instead of burning up in the ordinary way, was not so readily explained. To clear up this point, a set of experiments has lately been carried out, the results of which are given in a recent number of the Engineer.
The "service-boxes" in which the gun-cotton is kept are made of inch boards, and, when filled, the cover is tightly screwed on. Twenty-four such boxes were piled in a light wooden hut, similar in construction to the sheds in which gun-cotton is ordinarily stored, and twenty-four others were placed in a close-built brick magazine. Two boxes in each building were left partially open to facilitate ignition of the cotton. The wood hut was ignited by a bonfire of shavings, cotton, and petroleum. It smouldered for about seven and a half minutes, and then broke into the full characteristic gun-cotton flame, when in nine seconds more explosion took place. The cotton in the brick magazine was next ignited; smouldering followed for one minute, fierce gun-cotton flame for ten seconds, then an explosion. Experiments with the wood hut were afterward tried, with the cotton in light wooden boxes, and the lids partially open. It burnt in every experiment without explosion. The results are thus summed up: "Gun-cotton in service-boxes, packed in a close brick magazine, when ignited exploded; gun-cotton in service-boxes tightly screwed down, packed in a wooden hut, exploded; gun-cotton packed in light ½-in. boxes, with lids only partly screwed on and left partly loose, packed in a wood hut, burnt without explosion twice. The same experiment, differing only in the cotton being damped, caused no explosion." The inference therefore is, that confinement of the gases generated by burning, in tight, strong, wooden boxes, was the cause of the explosions, as, when not so confined, the burning went on as in the open air. "Apparently, the tendency of the experiments is to recommend, as the condition likely to be safest against explosion, that boxes should not be tightly closed or packed in high piles."
Culture of Wild-Plants.—A daughter of Dr. Lockwood, of Freehold, N. J., planted last year in the garden a root of the wild-violet, known to botanists as Viola sagittata. It had, during the first ten days of May of this year, borne over three hundred flowers, and was at that date a mass of cerulean bloom, with prospect of producing as many hundred more of flowers. The great advantage of this violet is, that its leaves do not grow so high in generous culture as do those of the species V. cuculata, or its variety V. palmata. Hence the luxuriant mass of flowers is always uppermost, and the rich blue is thus kept conspicuous. This same young lady, at the Monmouth County Fair last year, exhibited a case of living and growing wild-plants under the name "A Cryptogam Garden," which elicited great admiration. It was composed of rare indigenous ferns, all gathered in the wilds of the county. Among these was that graceful rarity, the climbing fern, Lygodium palmatum. There were mosses and lichens, and fungi of recherché forms and brilliant colors. The effect was very fine, and showed how rich are the resources at hand where there is a little taste to turn them to account.
Chameleonization in Frogs and Reptiles.—We published, in a previous number, a
