544 



EEPOET 1880. 



of which represent increments of Tolume, or, ia other words, of weight of fluid 

 displaced, the zero line or line corresponding to a ball in a liquid of equal density 

 to that of the ball, being previously traced out hy revohiug the drum "wathout 

 attaching the ball of metal itself to the spring, but with all other auxiliary attach- 

 ments. By a simple adjustment the ball is kept constantly depressed to the same 

 extent below the surface of the liquid, and the ordinate of this pencil line, measiu"ing 

 from the line of equilibriimi, thus gives an exact measure of the floating or sinking 

 efiect. 



If the weight and speciflc gra\'itv of the ball be taken when cold, we then have 



W D 



sufficient data for determming the density of the fluid metal for =— = —^ the 



volumes being equal. And remembering that W (weight of liquid) = W (weight 

 of ball), -I- .V (where x is always measured as a + or — floating efiect), we have 

 _ B' X (W^ + x) 



D (density of fluid) 



W 



The follo'^ving table shows the results of six experiments made by the authors 

 ia the laboratory of the Royal Mint. The bismuth was kept just above its melting 

 point, and this was ensured by placmg pieces of metal in the molten mass which 

 were observed just to melt. 



Mean, 10-055. 

 Specific gravity of solid bismuth, 9-82. 



It will be seen that, considering the difEcidties of manipulation, the results are 

 remarkably concordant, and their mean agrees very closely -with that obtained by 

 Mallet's method. We venture to think, therefore, that the amoimt of the change 

 of density of bismuth in passing from the solid to ' the fluid state may now be 

 considered to be definitely settled. 



6. On Crystals of Mercury. By Philip Braham, F.C.8. 



7. On a New Process for the Metallurgic Treatment of Complex Ores 

 containing Zinc. By Edwakd A. Parnell, F.C.S. 



The presence of zinc in considerable quantity in ores containing lead, copper, and 

 silver, is a great impediment to the extraction of the latter more valuable metals by 

 the ordinary smelting processes, and thus tends to reduce considerably the value of 

 such ores to the smelter. Immense quantities of these complex ores exist in 

 which the zinc (present as sulphide of zinc or blende) is so intimately mixed with 

 the sulphides of other metals that it cannot be separated by mechanical means 

 "dressing'). These ores have hitherto remained unproductive, because the 

 highest price offered for them by the smelter would not be remunerative to the 

 miner. By a peculiar combination, however, of wet and dry processes, such ores 



