Vol 12 Iss. 3

Generalizing the Catalan problem about the motion of a point rotating on a polished surface, the author searches for surfaces that allow the motion of a point rotating in a spiral with a vertical axis in the presence of friction, and explores the nature of the stability of the motion of a rotating point on a spiral located on a rough helical surface with a vertical axis, as well as the influence on this motion of the resistance of the medium, depending on speed, and the rotation of the surface around aerodynamic propellers.

Currently, to study the shape, size, deformations and movements of various bodies, their perspective photography is widely used, which served as the beginning of a number of new sciences, such as aerial photography and cinematography. This work is an introduction to the theory of the mentioned methods and contains elements of measuring perspective, i.e., solving metric problems in perspective. In addition to the specified practical goal, the methodological goal of the work is to use the coordinate method to systematically solve the main problems of descriptive geometry using the conical projection method. In accordance with the above, this work is divided into two parts: the first includes the basic principles of the conical projection method and methods for solving metric problems, and the second contains a number of solutions to typical examples that can be used in presenting a course in descriptive geometry.

In this paper is shown a practical possibility to perform flotation in a non-aqueous medium (petroleum, xylol, benzol), wherewith it is pointed out that a series of flotation phenomena, as compared with flotation in water, go in a quite contrary direction. Thus, hydrophilic minerals, as sodium chloride, quartz, are floated well, but the more hydrophobic pyrite can’t be floated. It has also been found that usually employed collecting reagents are unfit for flotation in non-aqueous medium. In the present experiments have been employed alcohols of the saturated series as collecting reagents, other collectors having not been found. It is stated that the quantity of alcohols necessary for the experiment is very great and that the consumption of them depends on the magnitude of the radical of the alcohol molecule and on the degree of humidity of the alcohol. As to other factors – character of froth-formation, influence of pulp density, time of agitation, etc. – there exists an analogy with flotation in aqueous medium.

By means of numerous examples taken from experimental work the author shows the falsity of the view which considers organic protective colloids as flotation poisons or in any case as substances possessing only the function of depressing minerals in flotation. It has been found that such colloid as casein possesses good collecting properties with respect to quartz, feldspar, apatite, and does not collect sulphides. Gelatine has analogous properties. Tannin has proved to be a selectively acting depressor with respect to galena, but not depressing zinc-blende, chalcopyrite, and other sulphides under the same conditions. By means of protective organic colloids it has been found possible to satisfactorily divide many mixtures of minerals, both sulphides and non-sulphides. These so interesting properties of organic colloids in flotation, discovered when studying them more closely, bear witness to the necessity of undertaking systematical investigations of this question.

This work gives the definition of the coefficient of resistance of the ventilating ducts as well as of the influence on the value of this coefficient of the curve of the interior and exterior angles of bending, of the grade of widening and of the sloping of the interior angle. It contains also the curves for calculating the coefficient of resistance of all kind of bending. The meaning of coefficients of resistance with the simultaneous expansion of air should be taken on the base of curves represented on fig. 2 and 3. Interior and exterior angles of turns should have rounded edges. The coefficients of resistance in this case also can be seen on the curves shown on fig. 2 and 3. It is recommended to the interior angles of turns. The size of the cut and the coefficients of resistance for this case should be taken on the curve, given on fig. 6. If the shaft is used for the purpose of ventilation only and is not used for hoisting then it is rational to lock the part of the shaft located above the air channel of ventilator.

Having in view the achievements of the mining operations with the aid of power shovels in the mountains Magnitnaya and Vysokaya and in the Elenovsky quarries, the present paper analyzes the following principal conditions for organizing power shovels operations: conditions concerning the design of machines; conditions with respect to the distribution of the serving personnel; conditions for the corresponding organization of drilling and blasting operations; conditions with regard to the corresponding organization of the transport. In the analysis of the conditions concerning the design of machines attention is drawn to the best manner of utilizing the available digging radius on the plane of the standing level of the power shovel, as well as increasing the maximum value of this radius by reducing the angle of inclination of the boom. In the analysis of the conditions concerning the methods of mastering the running of the machine attention is paid to the manner of filling the bucket and to the duration of the cycle of digging. In the analysis of the conditions with respect to the distribution of the serving personnel are given essential directions as to the duties of every worker serving the power shovel. In the analysis of the conditions of organizing drilling and blasting operations attention is drawn to the advantage of obtaining a concentrated well heaped stope of the blown up mass as uniformly crushed as possible. In the analysis of the conditions of organizing the transport attention is drawn to the means of securing an uninterrupted service of empty cars to be loaded.

In the summer of 1937 the author of this paper had an opportunity of observing horizons of crumpled brecciated rocks (7 to 12 meters in width) in the midst of quiet undisturbed Senonian limestones. The fauna gathered in this horizon shows that we are here in presence of upper layers of the Campanian stage. The character of the horizons of the brecciated rocks indicates that they originated during the period of stratification. Apparently a sliding down of sediments took place here when they were yet in a plastic state, which was accompanied by washing out. There often appear, in the hanging wall of the breccia horizon, fine pebbles or layers of conglomerate (up to 1 meter in width). The fragmental material met with here consists of the same limestones. The cause of the sliding down of sediments the author sees in the change of the slope of the bottom of the basin under the influence of tectonic movements. In these cases different portions of the bottom were uplifted above the sea-level, were washed out and gave coarse fragmental material. Many investigators admit the probability of an increase in tectonic movements by that time. V. V. Belousov (2) adduces arguments in support of the opinion that in regions of development of dome-shaped fields (whereto the north-eastern part of Daghestan also belongs) a slow growth of domes took place. He is of opinion that dome-forming commenced at the beginning of the Upper Cretaceous time, that is considerably in advance of folding. The author of the present paper supposes that such domes were just those upheavals along the slopes of which sediments slided. In the subsequent folding the anticlinal folds arrange themselves conformably to the position of the domes. Slide breccias coincide usually with synclinal zones and are absent in the crests of anticlines. In the vaults of anticlines, we sometimes meet with a seeming disappearance of horizons and with local unconformities.

The main library of the Leningrad Mining Institute was founded in 1773 together with the institute and is one of the oldest and largest technical libraries not only in Leningrad but in the whole USSR. It possesses a great book treasure, which is particularly rich in valuable journals published over many years up to the present, as well as in other modern periodicals. In the history of the library, two periods can be clearly distinguished: the first from the year of foundation until 1917, the year of the October Revolution; the second from the post-revolutionary period to the present day. In the first period, the library was accessible only to a narrow circle of specialists – professors and, in extreme emergencies, diploma students; students had no access. For them, there existed a small textbook library of a few hundred textbooks, which was open only three times a week for 1.5-2 hours. The library presents a completely different picture in the second period, but only from 1921 onwards. A reading room was opened for students, the textbook library was significantly enlarged and transferred to the main library. The outdated catalogues were replaced by new ones corresponding to modern requirements. The periodicals department was completely reorganised. To give a vivid picture of the growth of the main library, we cite the following data: in 1910, its book stock amounted to 80,000 volumes. On 1 January 1938 - 224,000 volumes. In 1910, the library was visited by 10,000 readers. In 1937 - by 150,017 readers. These figures speak for themselves and require no further explanation.