MISCELLANY. 



7S7 



those ingredients which are required for the 

 formation or healthy life" of the plant- 

 tissues. In " IIow Crops Grow," the evi- 

 dence is given which forces us to the conclu- 

 sion that silica is unessential to the growth 

 and perfect development not only of legumi- 

 nous plants, but of all the various cereals, 

 although the latter, when they grow in the 

 soil, do contain 2.5 per cent., more or less, 

 of this substance in their foliage. If silica 

 be taken up by legumes and by corn-crops 

 which are able to grow to perfection of 

 parts and fulness of dimensions in its ab- 

 sence, then, certainly, " because the tissues 

 want silica is no explanation of how they get 

 it ; " but saturation of the cell-juices does 

 explain how a limit is put to the influx of 

 this body into the plant from the soil. 



S. W. Johnson. 



Probable Cause of Boiler-Explosions. 



Some six years ago, Mr. W. F. Barrett, 

 F. C. S., observed that a red-hot ball of cop- 

 per, on being immersed in a light solution 

 of soap in water, entered the liquid without 

 hissing or visible generation of steam. In 

 a paper read before the British Association, 

 he tells of sundry experiments, made with a 

 view to investigate this phenomenon, and 

 thinks that it probably accounts for many 

 otherwise unaccountable explosions of 

 steam-boilers. After experimenting with 

 sundry red-hot metals in soap-water, he 

 tried water without soap ; but then the hiss- 

 ing was loud, and the evolution of steam 

 copious. He next dissolved in water sev- 

 eral soluble substances, and found that al- 

 bumen, glycerine, and organic liquids in 

 general, facilitate the acquisition by water 

 of the spheroidal shape, probably by in- 

 creasing its cohesion, while bodies such as 

 ammonia, which yield vapor readily, have 

 the same effect, though in not so marked a 

 degree. Oil, whether shaken up or floating 

 on the water, has the same effect as soap. 

 When the red-hot ball is lowered into the 

 liquid, to a depth of a foot or more, it is 

 seen to be surrounded by a shell, of vapor, 

 bounded by an envelop resembling bur- 

 nished silver. As the ball cools, the shell 

 grows thinner, and finally collapses. This 

 is followed by a report, and volumes of 

 steam are emitted. The author adds : " I 

 have heard that traces of oil get into the 



boilers of steam-engines, and there can be 

 no doubt that dissolved organic matter of- 

 ten finds its way in. If in any way we in- 

 crease the intensity of the water, we render 

 it possible for a corroded boiler to give way 

 under the pressure of the steam suddenly 

 generated in the way I have indicated." 



Practical Application of Ringing Flames. 



The " singing flame," which at first view 

 might seem to be merely a curious phe- 

 nomenon, is found to be, in fact, a discovery 

 of very high importance for science and the 

 useful arts. One of the latest applications 

 of this principle is that made by Dr. A. K. 

 Irvine, of the British Iron and Steel Insti- 

 tute, who makes use of the singing flame in 

 the construction of a safety-lamp for mines. 

 If an explosive mixture of inflammable gas 

 and air be passed through and ignited on 

 the surface of a disk of wire gauze too fine 

 to suffer the flame to traverse it, and then 

 surrounded by a chimney, to prevent air 

 from entering, save through the gauze, the 

 flame vibrates, and, the vibration being 

 communicated to the ascending gases, pro- 

 duces a sound varying in pitch and intensi- 

 ty according to the height and calibre of 

 the chimney. A lamp constructed on this 

 principle will give timely warning to the 

 miner whenever the atmosphere and the 

 fire-damp are coming together in the pro- 

 portions requisite for an explosion. 



Science in the Household. The applica- 

 tion of science to the affairs of the house- 

 hold, both in the shape of improved pro- 

 cesses and the introduction of labor-saving 

 appliances, has already gone sufficiently far 

 to warrant the expectation that from this 

 quarter there will eventually come a solu- 

 tion of the problem of rational house-keep- 

 ing, when the family will be largely rid of 

 the annoyances incident to a state of de- 

 pendence on incompetent and wasteful hire- 

 lings, and master of its own internal econ- 

 omy. Already the sewing-machine has 

 wrought a revolution in the clothing depart- 

 ment, which leaves scarcely a trace of its 

 former wearisome tasks. The washing-ma- 

 chine and wringer, aided by various deter- 

 gent preparations, have in like manner 

 greatly lightened the woifc of the laundry, 

 making the destructive and exhausting labor 



