of the various designs of separators. Methods of treatment at some of the largest magnetic mills in the United States are briefly described and illustrated by diagrammatic plans.-G. G. A.

Development of Ore-Concentration. HENRY A. MARVIN. Engineering Magazine, New York, 1915, vol. 49, pp. 218-230.-The Author deals with copper-milling and describes the early form of concentrating-table, on which model all modern concentration-plants have been built. Most of these make use of water as a medium through which the separation of valuable mineral-bearing grains from barren grains is effected by the difference in the rate of settling through the water. The newest method, called flotation, may be described as concentration reversed, and is based on that property of sulphides which makes them difficult to wet and on their tendency to float when dry. The use of static electricity and electro-magnetic separation is also mentioned. There are many

illustrations.-C. O. B.

Progress in Ore-Crushing Machinery.-J. I. WILE.-Engineering and Mining Journal, New York, 1915, vol. 99, pp. 691–694. ---The constant effort to make low-grade ores profitably workable is bringing about changes in the types of machines used for crushing. The time-honoured stamp is being displaced in American practice, for all but the toughest ores, by improved designs of disk-grinder, rolls, ball-mill and tube-mill, adapted in form and dimensions to each class of ore. The Author discusses these recently-modified forms, compares them for efficiency and cost of working, and shows their application in many cases.- -G. G. A.

New Chloridizing-Leaching Practice.-G. A. KEEP.-Engineering and Mining Journal, New York, 1915, vol. 99, pp. 265-269.— A new chloridizing-leaching process, in successful working at Park City, Utah, marks another advance in metallurgical operations. The roasting is effected by forcing a blast of air through an intimate mixture of ore, fuel and salt, moistened with water. The more efficient chloridizing and the prevention of waste by volatilization make it profitable to treat low-grade complex ores. The Author gives working details of the operations and technical control of the process. The article is illustrated.-G. G. A.

Roll-Pressure in Cold-Rolling Brass.-W. K. SHEPARD and G. C. GERNER.-American Machinist, New York, 1915, vol. 42, pp. 461-464.-Strips of annealed and unannealed brass of different thicknesses and widths were passed through rolls, and the pressure was measured by means of a testing-machine. The effect of speed of the rolls was investigated and found to be negligible. Compressive tests were also made, and the combined results are given in tabular statements and by means of graphs, by which it is possible to deduce the pressure on the rolls in any particular case, -H. R. S.

Magnetic and Other Properties of Electrolytic Iron melted in Vacuo.-T. D. YENSEN.-Proceedings of the American Institute of Electrical Engineers, New York, 1915, vol. 34, pp. 237-261.— Experiments made with electrolytic iron of 99.97 to 99.98 per cent. purity and fused in magnesia-crucibles are described and compared with results obtained with the best types of market transformer-iron. It was found that if melted in an atmosphere of CO inferior magnetic qualities were obtained, but if melted in vacuo these qualities were much enhanced. Swedish iron was also much improved by melting in vacuo. Methods of testing are described and the results given in tabular form and graphically. Microphotographs show the effect on the structure. The maximum permeability of commercial Swedish iron is given as 4,870; the same metal melted in vacuo gave 10,350, and electrolytic iron melted in vacuo 19,000.-H. R. S.

Recent Developments in Cast-Iron Manufacture.-J. E. JOHNSON, jun. Journal of the Franklin Institute, Philadelphia, 1915, vol. 179, pp. 59-93 and 171-213.-Recent improvements in foundrypractice are studied by means of an iron-carbon chart. The effect on the formation of graphite and other structural changes due to the presence of silicon, sulphur, phosphorus, titanium and vanadium, etc., are studied. The effect of oxygen, contrary to the usual belief, is shown to be highly beneficial, oxygen retarding the formation of graphite until the temperature of the metal is too low to admit of the production of flakes so that graphite nodules are formed, the resulting structure being stronger. This view is supported by photomicrographs. It is suggested that the known strength of coldblast iron is caused by the low temperature in the blast-furnace favouring the retention of oxygen.-H. R. S.

Deteriorating Effect of Wood Concrete on Iron Conduits.— Dr. W.LULOFS, M.Sc.-De Ingenieur, The Hague, 1914, vol. 29, pp. 840 and 889.—The deterioration of steel conduits laid in wood concrete, wood granite, xylolite, litosilo, or sgea, was on analysis found to be due to the presence of 9.46 per cent. of magnesium chloride, which causes the formation of iron chloride. Owing to the hygroscopic nature of the material, the water present further deteriorated the iron, so that the residue consisted of 32·53 per cent. iron carbonate and 64 64 per cent. iron oxide. Elimination of magnesium chloride as a preventive is suggested.-H. C. A. T.

German Standard Corrugated Sheets.'-Zeitschrift des Vereines deutscher Ingenieure, Berlin, 1915, vol. 59, pp. 224-229.-These standard specifications give the sizes of standard corrugated sheets of 60 millimetres width by 20 millimetres height up to 100 by 100 millimetres. Standard thickness and width, cross section per metre-width, weight in kilograms per square metre, moment of

Drawn up by the Verein deutscher Eisenhüttenleute.

resistance per metre-width, and safe loads for various free spans are also given. A formula for curved roofs is given, the theoretical basis of which is justified by Professor Siegmund Müller in a separate article.-H. C. A. T.'

Heat-Treating Equipment and Methods for Mass-Production. -E. A. SUVERKROP.-American Machinist, New York, 1915, vol. 42, pp. 725-730.-A detailed and illustrated description is given of the Heat-Treating Department of the Brown-Lipe-Chapin Company, Syracuse. The method of packing the pieces in the crucibles is described and each article is stamped with a number enabling the processes to which it has been submitted to be identified. A testpiece is placed on the top of each pot, from which it can be inferred whether further treatment is necessary. After quenching the articles are re-heated in a Gleason tempering-machine. The articles are placed in dies to prevent distortion whilst tempering.-H. R. S.

Modern Steels and their Heat-Treatment.-R. R. ABBOTT.— Journal of the Franklin Institute, Philadelphia, 1915, vol. 159, pp. 415-438.-The Author shows the varying structure of plain carbonsteels due to increase in the percentage of carbon by means of microphotographs, and thereby explains the increase of strength and the reduction in ductility. The effect of heating and quenching at various temperatures is similarly considered. The increase in martinsite in 0.2 per cent. carbon-steel as the quenching temperature is increased is shown by microphotographs, as well as the various stages of the change of martinsite into troostite.-H. R. S.

Growth and Distortion of Steel during Hardening. Dr. ING. E. H. SCHULZ.-Zeitschrift des Vereines deutscher Ingenieure, Berlin, 1915, vol. 59, pp. 66-71, 112–116.-These experiments show that water-hardened steel decreases in volume by reheating, the maximum density being obtained at 800° F., and the higher the percentage of carbon the greater will be this decrease. Comparisons are made between the distortion of oil- and water-hardened steel. A graphic study of the distortion of various steels is given. The addition of nickel or other substances reduces the distortion. Tables and microphotographs accompany the article.-H. C. A. T.

Factors in Hardening Tool-Steel.-J. A. MATHEWS and H. J. STAGG, jun.―Journal of the American Society of Mechanical Engineers, New York, 1915, vol. 37, pp. 141–147. The practical side of hardening and tempering tool-steel is considered. The time of heating is of extreme importance. If too short in a hot furnace, the edges and thin parts are overheated. If the time is too long, large grains are formed throughout the mass. The effect of the mass on hardness was investigated by making Brinell tests and the results are plotted, and from them a curve is obtained giving the quenching temperature for various diameters.-H. R. S.

1 See Zeitschrift des Vereines deutscher Ingenieure, vol. 59, pp. 226-229.

Hardness-Tests of Cold-rolled Steel.-W. K. SHEPARD and C. T. PORTER.-American Machinist, New York, 1915, vol. 42, pp. 277–278.-Tests made with plain sheet steel, 0.1 to 0.35 inch thick, were undertaken to determine the relation, if any, between the ultimate tensile strength and the Brinell and scleroscope hardness-numbers. On plotting the Brinell numbers against ultimate tensile strength, the observation-points were found to lie sensibly in one straight line for all percentages of carbon-content, for which the equation is given. In the case of the scleroscope numbers, however, the plotted points were found to be ranged on different straight lines for each percentage of carbon-content.-H. R. S.

Experiments on Elastic Hysteresis.-Dr. R. GRAMMEL.-Zeitschrift des Vereines deutscher Ingenieure, Berlin, 1914, vol. 58, pp. 1600-1602.—By the application and relaxation of tensile or compressive stress an elastic-hysteresis diagram may be obtained. The Author found that: (1) Hysteresis-losses are independent of the frequency of the cycle of operation; (2) energy-losses are exactly proportional to the third power of the maximum stress and eight times greater for soft steel than for hardened steel.— H. C. A. T.

Recent Siemens-Martin Steel-Works.-H. HERMANNS.-Zeitschrift des Vereines deutscher Ingenieure, Berlin, 1914, vol. 58, pp. 1493–1501.—-Following Great Britain and the United States, Germany is replacing Bessemer and Thomas plants by SiemensMartin furnaces of modern design. The advantages of the latter are reduced first-cost, introduction of labour-saving machines, and improved means of conveying raw material to the furnace and thence to the mills. The chief feature of the article is a detailed description of modern plants illustrating these points.-H. C. A. T.

Metal-Spray Processes in Engineering and Art.-J. CALDER.— Journal of the American Society of Mechanical Engineers, New York, 1915, vol. 37, pp. 378–383. Various methods for spraying metals are described, including an early one in which molten metal was atomized. Finely-powdered metal-dust can also be forced through a heated nozzle by air-pressure, and it is stated that large surfaces, such as bridge-members, can thus be protected, using zinc-dust The modern method, using a "spraying-pistol," in which a wire of the metal to be sprayed is automatically fed into an oxy-gas blowpipe, is fully described and illustrated. There are Tables of costs for eight different kinds of metal.-H. R. S.

Oxyacetylene Welding.'-Engineering and Mining Journal, New York, 1915, vol. 99, pp. 393–397.-The suitability of oxyacetylene welding to repair-work is being recognized by the large mining companies of the United States. Probably the largest repair-job

See also Minutes of Proceedings Inst. C.E., vol. cxcvii, p. 368, and vol. cxcviii, p. 418.

yet attempted has been successfully accomplished by the Anaconda Company in renovating its main dust-flue, work which involved 10 miles of welding. This and other large jobs of different character are described, and in some instances the cost is worked out. Concerning the strength of these welds opinions differ. The article is illustrated.-G. G. A.

1

Welding the Joints of Steel Gas-Mains.-Engineering News, New York, 1915, vol. 73, pp. 233–234.-The Author explains the application of the oxyacetylene process to the joining up of wrought-iron or steel pipes to make a continuous line, and gives a Table of costs. Pipes 40 feet long may be welded into a continuous section up to 4,000 feet and then lowered into the trench. Photographs show the method of welding and lowering pipes into the trench.-C. O. B.

Making Steam-Headers and Steam-Separators by the Oxyacetylene Method.--R. MAWSON.-American Machinist, New York, 1914, vol. 41, pp. 725-728.-Several examples, photographically illustrated, are given of steam-separators and steam-headers in which the branches and the flanges have been welded on by the oxyacetylene flame. In a steam-separator internal baffles were welded before the ends were welded on. A section shows that when a branch is welded on to a body the connection is correctly bell-mouthed. Examples are also given of 2- and 3-inch pipes 40 feet long with the coupling-flanges welded on for a working pressure of 2,000 lbs. per square inch.-H. R. S.

Mode of Working the Rare Earths in Brazil. -JACQUES BOYER. -La Nature, Paris, 1915, part 1, pp. 324–326. It is shown that the extraction of thorium, cerium and other products, termed rare earths, has hitherto been an industry largely in German hands. Some account is given of the method of working the monazite sands of Brazil, now carried on by the Franco-Brazilian Company, and this Company also conducts the treatment of thorium nitrate found in Norway. A whole series of salts and oxides of the rare earths, of which a list is given, are being manufactured in France.-G. R. R.

Chilian Nitrate-Industry.-M. R. LAMB.-Engineering and Mining Journal, New York, 1915, vol. 99, pp. 811-815.-Nitrate mining on the West Coast of Chili supplies the world with 3,000,000 tons of sodium nitrate annually. To increase this source of supply by making the working of low-grade ores profitable is the problem of this industry. The leaching process by which the nitrate is extracted, though simple and cheap, is in many ways wasteful. New processes, favoured by two schools, are suggested, whereby practically all the nitrate may be extracted. Principles and method of working are discussed in detail. The article is illustrated.-G. G. A.

1 See Minutes of Proceedings Inst. C.E., vol. cxevii, p. 368, and vol. cxeviii, P. 418.