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THE POPULAR SCIENCE MONTHLY. 



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 cohe- 

 sion. 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. Rome, 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 oc- 

 curred at Stowmarket, in England, some- 

 thing 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 ordi- 

 narily 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 shav- 

 ings, 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 ex- 

 plosion 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 after- 

 ward 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-cot- 

 ton in service-boxes tightly screwed down, 

 packed in a wooden hut, exploded ; gun- 

 cotton packed in light |-in. boxes, with lids 

 only partly screwed on and left partly loose, 

 packed in a wood hut, burnt without explo- 

 sion 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 explo- 

 sion, that boxes should not be tightly closed 

 or packed in high piles." 



Cnlture 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 advan- 

 tage 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 va- 

 riety V. palmata. Hence the luxuriant mas8 

 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 recherche forms and brilliant 

 colors. The effect was very fine, and 

 showed how rich are the resources a't hand 

 where there is a little taste to turn them to 

 account. 



Chameleon ization in Frogs and Reptiles. 



We published, in a previous number, a 



