The buoy is filled through an aperture, k, in the side of the upper tube. This aperture is provided with a valve which allows of the buoy being charged by connecting it with the accumulators located on a boat built especially for this service. As soon as the gas reaches 6 or 7 atmospheres the cocks of the buoy and reservoir are closed, and the connecting tube is removed. The consumption of gas in the lantern is. 1,230 cubic inches per hour. This being known it is very easy to calculate from the capacity of the buoy how often it is necessary to charge it. A large number of buoys on the Pintsch system are already in use. The oil gas is likewise applicable to the illumination of lighthouses, and among those that are now being lighted in that way we may cite the one in the port of Pillau, near Königsberg. Several large steamers are likewise being lighted on this plan. In such an application of oil gas the management of the apparatus is very easy, and the permanence of the illuminating power of the gas gives every facility for the lighting of the boat, whatever be the duration of the trip. Although Mr. Pintsch's process of manufacture has been but recently introduced into France, it has received a number of applications that permits us to foresee the future that is in store for it. The Railway Company of the West has contracted for the lighting of 250 first-class cars that run within the precincts of the city; the State Railways have 56 cars lighted in this way running between Nantes and Bordeaux and between Saintes and Limoges; and the Line of the East has just applied the system to 80 of its cars. * * * * * DELICATE TEST FOR OXYGEN. T. W. Engelmann proposes, in the _Botanische Zeitung_, a new test, of an extremely delicate nature, for determining the presence of very minute quantities of oxygen, namely: its power of exciting the motility of bacteria. If any of the smaller species, especially _Bacterium termo_, are brought to rest, and then introduced into a fluid in which there is the minutest trace of free oxygen, they will immediately begin to move about freely; and if the oxygen is gradually introduced, their motion will be set up only in those parts of the drop which the oxygen reaches. In this way Engelmann was able to determine the evolution of oxygen by _Euglena_ and by chlorophyl granules. * * * * * DETERMINATION OF SMALL QUANTITIES OF ARSENIC IN SULPHUR. By H SCHÆPPI.