Page:Proceedings of the Royal Society of London Vol 4.djvu/172

Rh The rays, when reflected from an imperfect parabolic metallic mir- ror in a lantern, and collected into a focus by a glass lens, readily burned a hole in a paper at a distance of many feet from their source. The heat was quite intolerable to the hand held near the lantern. Paper steeped in nitrate of silver and afterwards dried, was speedily turned brown by this light : and when a piece of fine wire-gauze was held before it, the pattern of the latter appeared in white lines, corresponding to the parts which it protected. The phenomenon of the transfer of the charcoal from one electrode to the other, first observed by Dr. Hare, was abundantly apparent ; taking place from the zincode (or positive pole,) to the platinode, (or negative pole). The arch of flame between the electrodes was attracted or repelled by the poles of a magnet, according as the one or the other pole was held above or below it : and the repulsion was at times so great as to extinguish the flame. When the flame was drawn from the pole of the magnet itself, included in the circuit, it rotated in a beautiful manner.

The heating power of this battery was so great as to fuse, with the utmost readiness, a bar of platinum, one-eighth of an inch square : and the most infusible metals, such as pure rhodium, iridium, tita- nium, the native alloy of iridium and osmium, and the native ore of platinum, placed in a cavity scooped out of hard carbon, freely melted in considerable quantities.

In conclusion, the author briefly describes the results of some ex- periments on the evolution of the mixed gases from water in a con- fined space, and consequently under high pressure ; with a view to ascertain, first, in what manner conduction would be carried on, supposing that the tube in which the electrodes were introduced were quite filled with the electrolyte, and there were no space for the accumulation of the gases ; secondly, whether, decomposition having been efl*ected, recombination would take place at any given pressure ; and lastly, whether any reaction on the current-force of the battery would arise from the additional mechanical force which it would have to overcome. These experiments he purposes pur- suing at some future time.

A paper was also read, entitled, ** An experimental inquiry into the influence of nitrogen in promoting vegetable decomposition, and the connexion of this process with the growth of plants." By Robert Rigg, Esq. Communicated by the Rev. J. B. Reade, A.M., F.R.S.

The author considers it as a general fact, to which there are very few if any exceptions, that vegetable bodies in the state in which they are produced in nature, undergo spontaneous decomposition when kept under circumstances favouring such an action ; and that, from the decomposition of each, compound products peculiar to that substance result. A variety of experiments are detailed and tabu- lated ; the first series of which contains those made on solutions of compounds, such as sugar, honey and extract of malt, shovdng that in each the amount of spontaneous decomposition is in proportion