and with this well no chloride of calcium was observed until about two months after the gas had been struck. In these calculations of the heating power of gas and coal no account is of course taken of the loss of heat by radiation, etc. My object has been to compare these two fuels merely as regards their actual value in heat units." Bearing in mind that it is never wise to prophesy unless you know, I hesitate to speak of the future; but considering the experience we have had in regard to the productiveness of the oil territory, which is now yielding 70,000 barrels of petroleum per day, and which has continued to increase year after year for twenty years, I see no reason to doubt the opinion of experts that the territory which has already been proved to yield gas will suffice for at least the present generation in and about Pittsburg. * * * * * A GAS-ENGINE WATER-SUPPLY ALARM. [Illustration] A very useful contrivance for the purpose of reporting automatically the failure of the water supply to a gas-engine has been arranged by Professor Ph. Carl, of Munich. What led to the adoption of the device was that, during last winter, the water supply in the neighborhood of the Professor's laboratory was several times cut off without previous notice; the result being the failure of the water needed for cooling the cylinder of his Otto gas-engine. On inquiring into the matter, he discovered that the same thing frequently occurred in other places where gas-engines were in use; and this caused him to design a contrivance to put an alarm-bell into action at the instant when the water ceased to flow, and so enable any overheating of the engine, and injuries thereby resulting, to be prevented in time. The arrangement (represented half size in the accompanying engraving) is screwed down directly to the water outflow pipe, R. Before the aperture of the pipe is a lever, with a disk on one arm, on to which the issuing water impinges, thereby keeping the lever in the position indicated by the dotted lines. The effect of this is to break the platinum contact at C, and so interrupt the circuit of an alarm-bell placed in any suitable position. Suppose the water ceases to flow; the spring, F, comes into play, contact is made at C, and the bell continues to ring till some one comes to stop it. It is almost needless to remark that the disk, D, and the pin, E, are composed of insulating material, such as vulcanite.--_Jour. Gas Lighting._ * * * * * SOLDERING AND REPAIRING PLATINUM VESSELS IN THE LABORATORY. By J.W. PRATT, F.C.S.