smaller than the other, and in its centre. In the annular space left. between the two, the various gradations of color, from blue to pink, are arranged radially, which being accomplished and the degrees of moisture marked, :I. piece of the prepared paper is placed in the inner circle, and the changes which occur can be thus conveniently read.
Sodium as an Explosive Agent,*-A contemporary calls at-. tcntion to the fact that cxpcrimcnts upon the application of sodium a8 an explosive, which were originated, we believe, some years ago by Prof. Wurtz, of New York, are about to be recommenced. In this connection it may be interesting to describe briefly the ~tzoclus O~CTYZ& followed in these earlier experiments. The theory of the plan here proposed, rests upon the great expansive force which will be exercised upon tho walls of a vessel in a confined space, this force being readily called into operation by the hydrogen suddenly evolved in the decomposition of water by the sodium. The device by which this may be utilized in practice, is described as consisting of two glass bulbs which are blown with a neck between One bulb is filled with sodium, the other with water-while them. in the neck connecting them a soluble salt is previously fused. The time required to fire the charge can be regulated at pleasure by the varying size or length of the neck. With this arrangement the apparatus is lowered into the drill hole, the sodium being below. The salt is gradually dissolved by the water and as this comes into contact with the sodium the explosion ensues. In order to utilize the theoretical value of the charge it would be ncccssary that all the sodium should be expended in the decomposition of the water. How far this is accomplished in the arrangement just described, it is impossible to state with any certainty. But though it may bc found to operate with good effect, it is clear that but a fraction of the possible power can be thus obtained, as the explosion will ensue before the sodium is completely utilized. The principle is, however, ingenious, and with such improvements in its application which a few practical trisis will readily suggest, may prove in time a valuable addition to the art of blasting. The Nanufacture of Platinum.-In relation to this subject in one of the former issues of the Journal, the erroneous statement WAS, made that there was but one establishment in the country for the manufacture and working of platinum. The statement, we have * Jonrn.
App. Chew., Dec., 1811.