_Generator C Size_ (producing 2,500 cubic feet per hour): Anthracite to make gas at the rate of 2,500 s. d. cubic feet per hour=30 lb. x 9 working hours=270 lb. at 20s. a ton............ 2 4½ Allowance for wages of attendant....... 1 6 Repairs and depreciation of generator, gasholder, etc. (5 per cent, on £160)= per working day...................... 0 6½ Interest on capital outlay, ditto...... 0 6½ _______ Total......................... 4 11½ cub. ft. Gas produced........................... 22,500 Less gas used for generating and superheating steam................... 1,500 ______ Total effective gas for 4s. 11½d 21,000 Net cost, say, 2¾ d. per 1,000 cubic feet. * * * * * ON THE FLUID DENSITY OF CERTAIN METALS. [Footnote: Abstract of paper read before Section C (Chemical Science), British Association meeting, York.] By PROFESSOR W. CHANDLER ROBERTS, F.R.S., and T. WRIGHTSON. The authors described their experiments on the fluid density of metals made in continuation of those submitted to Section B at the Swansea meeting of the Association. Some time since one of the authors gave an account of the results of experiments made to determine the density of metallic silver, and of certain alloys of silver and copper when in a molten state. The method adopted was that devised by Mr. R. Mallet, and the details were as follows: A conical vessel of best thin Lowmoor plate (1 millimeter thick), about 16 centimeters in height, and having an internal volume of about 540 cubic centimeters, was weighed, first empty, and subsequently when filled with distilled water at a known temperature. The necessary data were thus afforded for accurately determining its capacity at the temperature of the air. Molten silver was then poured into it, the temperature at the time of pouring being ascertained by the calorimetric method. The precautions, as regards filling, pointed out by Mr. Mallet, were adopted; and as soon as the metal was quite cold, the cone with its contents was again weighed. Experiments were also made on the density of fluid bismuth; and two distinctive determinations gave the following results: 10.005 ) ) mean 10.039. 10.072 ) The invention of the oncosimeter, which was described by one of the authors in the "Journal of the Iron and Steel Institute" (No. II., 1879, p. 418), appeared to afford an opportunity for resuming the investigation on a new basis, more especially as the delicacy of the instrument had already been proved by experiments on a considerable scale for determining the density of fluid cast iron. The following is the principle on which this instrument acts: