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Editors of engineering periodicals usually read the advertising pages. It may be hard' for some men, let alone engineers, to understand what value there is in reading "dry advertisements." Yet it is a fact that valuable suggestions have been obtained from these so-called "dry advertisements" which have been the means of securing greater efficiency in the performance of some undertaking and consequent saving of time and money. It seems to be an editorial practice to look to the advertisements for suggestions for the reading pages. It is a fact that some of the most appreciated descriptive articles were suggested by advertisements. Every undertaking is limited to that point where tools and machinery for its successful performance and completion may be purchased or manufactured. No work can he planned without having in mind such limitation, and the technical journals may be relied upon to furnish descriptions, both editorially and through the advertising pages, of methods and plant used in successfully performing various tasks. This being so, why should not the reader or subscriber to a magazine or periodical avail himself of such a fountain of knowledge? Such perusal proves of value to the up-to-date engineer or man occupying a -position. of responsibility where initiative is essential. Authorities agree that advertisements are on a par with technical articles for their educational value, and this Is as it should be. Also, most subscribers to a publication realize that a, successful advertising medium means a continuance of advertising patronage, which in turn enables the publisher to turn out a better and larger volume of reading matter.

Jan 6, 1915

By R. S. Dean

True careful work of Gross and Zimmerley1 has established the fact that the energy actually used in grinding is proportional to the new sur-face produced. This confirmation of Rittinger's law was made by crush-ing quartz in a frictionless drop-weight machine and determining the surface of the quartz by its rate of solution in hydrofluoric acid. The details of this procedure have been described adequately elsewhere and need not be repeated here. The resultant data furnish the only available basis for comparing accurately the efficiency of grinding machines. This method is so cumbersome experimentally that it has been little used. As an alternative all sorts of approximations have been proposed. The best of these is complete size analysis by sieving and elutria-tion. Such procedure is very lengthy and difficult to carry out accurately. Furthermore, any sizing method becomes very inaccurate for determining surface with very fine sizes where the ratio of surface to volume becomes very large. To avoid the lengthy and difficult technique of elutriation it has been proposed to estimate the size distribution below 200 mesh from various probability formulas. Such a procedure is at best an engi-neering approximation; at worst it is a mere guess. Some time ago Dr. V. H. Gottschalk2 found that the coercive forces of magnetite powders were directly proportional to the surface area, regard-less of size distribution. It was at once apparent that this furnished a method for determining grinding efficiency quickly and accurately. The only requirement was a single determination of the relation between the work input of the Gross-Zimmerley drop-weight machine and the coercive force of the resultant crushed magnetite.

Jan 1, 1936

The Library of the above-named Societies is open from 9 A.M. to 10 P.M. on all week-days, except holidays, from September 1 to June 30, and from 9 A.M. to 6 P.M. during July and August. The Library contains about 55,000 volumes, including sets of technical periodicals and the publications of scientific and technical societies. Members of the Institute, with few exceptions, are forced to spend a portion of their time in localities isolated from sources of information. To these the Library can render valuable service through correspondence; letters requesting information will receive special attention. The Library is prepared to furnish references and copies of articles on mining and metallurgical subjects; to determine the existence of mining maps, and to furnish general information as to the geology and mineral resources of all countries. All communications should be made as definite as possible so that the information received may be what is desired and not include collateral matter which may not be of interest. The time spent in searching for such collateral matter will be saved, and the information will be sent more. promptly and in more usable shape. The members of the Institute can be of service to the Library by forwarding copies of mining reports, maps privately issued, and similar material, which will be classified, indexed, and made available to other members. Suggestions for additions to the Library, either by purchase or personal solicitation as gifts, will be welcomed. It is hoped that members while in the city will use the Library freely, and assurance is given that most careful service will be rendered to them.

Jan 12, 1914

By R. A. Brackett

The most effective means of controlling the dust in the drilling of rock has been found after careful investigation to be collection of this dust at the source. By direct collection, all the dust is collected at the collar of the drill hole and deposited into suitable containers. Equipment for handling this work can be either portable or stationary, depending upon the particular requirements and the application. For most work the portable unit is found most advantageous, and with a capacity capable of handling two drills operating simultaneously. Such a portable unit would consist of a metal cap, or hood, placed against the face of the rock through which the drill steel would be inserted. This hood is connected by a flexible rubber hose to a primary separator, where the bulk of the dust is collected. From here a second length of hose connects to the secondary stage of separation, where the fine particles of dust are collected and which is built in as an integral part of the vacuum producer. Hoods are adapted for vertical, horizontal or stope drilling, and mounted so as to become immediately effective when collaring the hole and remain in place continuously. Such dust collectors can be used with either wet or dry drilling. However, in view of the fact that when drilling dry and using the dust collector, the dust count can be maintained within safe limits, wet drilling becomes unnecessary. Furthermore, it has been found that when using the dust collector not only has the dust hazard been eliminated, but also increased footage can be obtained. Samples taken under a wide variation of conditions indicate that where the dust count required is below five million particles per cubic foot, dust collectors will be required. Opreators, in general, accept the use of this additional equipment favorably, and it is generally felt that such means of collecting the dust will soon be universally adopted. Tests made by the Connecticut Department of Health Bureau of Occupational Diseases show dust counts reduced from 203 million particles to 6.05 million by the use of the dust collector, when drilling dry.

Jan 1, 1934

By R. Adair, W. R. Hudspeth, W. T. McDaniel

D. C. Ralston (U. S. Bureau of Mines, Washington, D. C.)—Flake mica can be beneficiated by a wider variety of methods than almost any known mineral. However, most of these methods are not recorded. It is therefore a pleasure to find a written record of another application of a new method of beneficiation. The fact that the Humphries spiral gives a concentrate containing the mica flake mixed with the slime and small grit has forced a further separation by screening, in which the finest of the flake will pass through. Fine flake has its uses and if mixed with slimes or clay is recoverable reliably only by flotation. This loss must be charged against the spiral. On the other hand, the new muscovite mica paper recently brought out by General Electric Co., can be made only with grit free flake larger than 50 mesh. It is of interest to learn from the authors whether the washing of the flake on a 50 mesh screen can take the grit content below 1 pct, to meet this new demand. Must another degritting process be used on the flake, like electrostatic treatment of the dried material? H. D. Snedden (The Humphreys Investment Co., Denver)—When recovering mica in the spiral, gangue particles coarser than 16 mesh can be rejected more readily when operating at a high pulp density (35 pct solids) or a low volume rate (—15 gpm). A launder screen as used by Lehigh Coal Co. has proved very satisfactory to partially dewater the mica concentrate and to reject any gangue slimes it may contain. Under certain conditions mica cleaning in the spiral can be improved by reagentizing the spiral feed, the object being to insure wetting of the gangue minerals and to agglomerate or prevent wetting of the mica particles. R. B. Adair (authors' reply)—The grit content of the mica recovered on Humphreys Spirals varies with the fineness of the launder screen used to clean the mica product. Normal practice has been the use of 80 mesh screen, which will produce a mica product of acceptable grit content for most purposes. By using a 50 mesh screen, and increasing the screen area per ton of feed, it is felt by the authors that a mica of 99 pct plus purity could be obtained. This statement would hold only in the case of mica feed which was well de-laminated, and free from "clay balls," (semikaclinized feldspar), which tends to follow the mica through the process.

Jan 1, 1952

By Clyde Evarts Weed

SOME one once affirmed his great belief in luck, adding that he had found that the harder he worked the more luck he had. Clyde Weed is a firm believer in this method of courting the fugitive lady. He is at work early and late, often leaving his staff at Anaconda's offices at 25 Broadway breathless trying to keep up with the ideas teeming from a fertile brain and the actions those ideas entail. Miles ahead of his assistants much of the time, he still manages to be an agreeable fellow to work with, no small accomplishment as many can testify. Mr. Weed arrived in the world at Moorestown, Mich., on Aug. 8, 1890. Sixteen years later he entered Michigan Agricultural College, a lowly freshman. The following year, with the experience and wisdom expected of a sophomore, he transferred his studies from the reaping of a harvest on the surface of the earth to delving into the deeper, unpredictable bowels of the earth, his studies now shifted to the Michigan College of Mines. Last June his alma mater conferred upon him the degree of Doctor of Engineering.

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