DRYING OILS 101 



observations in a highly interesting memoir, entitled Preparation du Mineral d"Etain 

 dans Ic Cornwall, and also in the Annales des Mines, tome ix. 1866. But it is to 

 Germany we must look for an exhaustive literature on the Dressing of Ores, and ma- 

 chinery employed therein. In 1867, 1870, and 1873, Von Rittinger's Lehrbuch der 

 Aufbereitungskunde appeared, with an atlas, containing forty-nine plates. In 1872 

 Die Aufbereitung, by M. F. Gaetzschmann, with an atlas of sixty-six plates, was pub- 

 lished. In addition Hundt of Siegen, Neuerberg of Kalk, Cologne, Utsch of Iserlohn, 

 Hoffmann of Lohmansfeld, Max Braun of Altenberg, and many others have promoted 

 the science and art of Dressing. In England there are hopeful signs that the subject 

 will be deemed worthy the attention of Mine Engineers. Continuous machinery is in 

 operation at several mines, and its use somewhat extending. In South Australia 

 Hancock has successfully applied himself to the subject of continuous Dressing; 

 while in America the mechanical enrichment of minerals will necessarily command 

 much consideration. Too much attention cannot be given to this section of mining 

 economics ; for with the increasing production of ores, especially of ores of low pro- 

 duce, and the ill-adapted machinery oftentimes employed, the loss in concentrating 

 them is an item of most serious moment. 



In this paper we have included those machines which have been long employed in 

 our metalliferous mines, many of them having been proved by experience to be 

 most economical, together with such of the modern introductions as appear to 

 promise the most advantage, and some suggestions which cannot but be valuable, 

 since the principles involved are founded upon the universal laws of gravitation, 

 as applied to solids and fluids in motion. 



It is not essential to describe the dressing routine observable in a particular mine, 

 since it is scarcely possible to observe the same system in any two distinct concerns. 

 In the various modes of treatment, however, it may be remarked that the two leading 

 features will always be reduction to a proper size and separation of the ore from the 

 refuse. Until the vein-stuff arrives at the crusher or stamps, the labour is chiefly one 

 of picking and selecting ; but from these machines usually commence a long series of 

 divisions, subdivisions, selections, and rejections. To follow these out in their various 

 ramifications would not only exceed the limits of this paper, but would perhaps bo 

 misunderstood by those not intimately acquainted with the subject. J. D. 



DRUGGET is a coarse, but rather slight, woollen fabric, used for covering carpets., 

 and as an article of clothing by females of the poorer classes. 



The manufacture of druggets of various kinds has been of late years considerably 

 improved ; and carpets, many of them handsomely figured, are now found in common 

 use. 



DRUID-STONES. Masses of quartzose rock scattered as loose blocks over the 

 Chalk downs in the south of England, and known variously as Druid-stones, Sarsen- 

 stones, and Greyweathers. 



DRUSE. A mineralogical term, signifying a hollow space in veins of ore or in 

 rocks, which is lined with crystals. A drusy cavity is one covered with crystals. 



DRY BONE. A term sometimes applied by American miners to calamine or 

 carbonate of zinc. 



DRY GRINDING. The practice of employing dry stones has been long adopted 

 for the purpose of quickening the processes of sharpening and polishing steel goods. 

 The dry dust from the sand-stone, mixed with the fine particles of steel, being inhaled 

 by the workmen, produces diseases of the pulmonary organs to such an extent, that 

 needle and fork grinders are reported rarely to live beyond the ages of twenty-five or 

 thirty. 



Mr. Abraham, of Sheffield, first invented magnetic guards, which, being placed 

 close to the grindstone, attracted the particles of steel, and thus protected the men 

 from their influences. Still they suffered from the effects of the fine sand-dust, and 

 the grinders heedlessly abandoned the use of them altogether. 



Mr. Abraham devised another plan, which is employed, although only partially, in 

 the Sheffield works. The grindstone is enclosed in a wooden case, which only ex- 

 poses a portion of the edge of the stone ; a horizontal tube proceeds at a tangent from 

 the upper surface of the circle to the external atmosphere. The current of air gene- 

 rated by the stone in rapid revolution, escaping through the tube, carries off with it 

 nearly all the dust arising from the process. It is curious to find so simple a con- 

 trivance frequently rejected by the workmen, notwithstanding that sad experience 

 teaches them, that they are thereby exposing themselves to the influences of an atmo- 

 sphere which produces slowly but surely their dissolution. 



DRYING OIXiS. When oils, especially linseed and nut oils, are boiled with litharge 

 or oxide of lead, they acquire the property of solidifying or drying quickly on expo- 

 sure to the atmosphere. These are very useful to the painter, as without them the 

 pigments with which they are mixed would remain soft. The oxide of lead appears 



VOL. H. M 



