Polytechnic Association Proceedings. 839 



powder hilvgazintes. 

 The destructive effect of the late explosion of uitro-glycerine 

 near Jersey city, has turned attention to the importance of providing 

 a suitable place for the storage of explosive compounds. Mr. 

 Mallet, in commenting upon the Erith powder explosion, expresses 

 the opinion that great destruction is not likely to be caused by the 

 propagation of the shock of an explosion through the earth, except 

 v'ilhin a very limited area. To protect the neighborhood against 

 the aerial wave, he suggests the construction of a permanent circular 

 travers or bank, at such distance, and of such inclination as not to 

 be shaken by the earth shock of an explosion, and raised high 

 enough to shield buildings without; in other words, that the posi- 

 tion of the magazine should be at the center of an inverted conic 

 frustum. 



THE EFFECT OF SOUND ON WATER-JETS. 



We noticed, not long since, the beautiful philosophical experi- 

 ment which illustrates the effect of sonorous vibrations on the 

 ordinary gas flame. Prof. Tyndall, of the Royal Institution, Lon- 

 don, has repeated on a large scale an experiment of Savart's, 

 showing the influence of sonorous air-waves on a jet of water. 

 Water was discharged obliquely from an ordinary gas burner. By 

 the aid of an electric lamp, a shadow of the vein, as it broke iuta 

 scattered drops, was thrown upon a large white screen. On sound- 

 ing an organ-pipe, or a steel tuning-fork of proper pitch, the drops 

 would reunite in a continuous stream, and form on the screen a band 

 several feet in length. When the sound ceased, the vein again 

 broke into drops. The minuteness of the force required to pro- 

 duce this effect was shown by placing a tuning-fork, just after its 

 vibrations had ceased to be heard, against the support of the nipple 

 from which the water issued, when the di-ops would instantly 

 coalesce. The jet was equally sensitive to beats, and the eye and 

 ear gave proof of a perfect synchronism. 



FUNCTIONS OF THE ROOT. 



M. Corenwinder read the memoir before the French Academy 

 of Sciences on the functions of the roots of vegetables, in which he 

 concludes from experiments made by him that the root does not 

 obtain, by absorption, all the carbonic acid found in it. On putting 

 the roots in communication with a certain proportion of this acid, 

 either in a gaseous state, or in solution in water,, he invariably found 



