Materials on the Study of the Kursk Magnetic Anomaly, published under the editorship of Acad. P. P. Lazarev:

Issue 1. Report of the Commission for 1919. Moscow, 1920, pp. 60.
Issue 2. Prof. E. E. Leyst. The Kursk Magnetic Anomaly. Moscow, 1921, pp. 72.

Acad. P. Lazarev. The Kursk Magnetic Anomaly. (Uspekhi fizicheskikh nauk, vol. II, issue 1.)

The magnetic anomaly in Kursk Province has more than once attracted the attention of a number of investigators; Prof. E. E. Leyst devoted especially much labor to its study. Beginning in 1894, the latter carried out systematic measurements in this region; in all he made observations at 4,121 points.

The work was completed, the materials processed, maps drawn up, and the results were reported at colloquia in the Geophysical Institute of Moscow University and in the Physical Institute of the M. S. S. Prof. Leyst died in 1918 in Germany; with his death all the maps and catalogs of observations disappeared, and only the written report remained, which has now been printed on 72 pages. Here only the general dimensions and direction of the anomalous regions are determined, of which there proved to be two; between them extends an area free of large anomalies, up to 60 kilometers wide; a general description is also given of the distribution of isogons, isoclines, and isodynamic lines—\(H\) and \(Z\). It turned out that the anomalies represent a series of nest-like areas, for the most part arranged in rows.

The value of \(Z\) reaches as much as \(19.135\ \Gamma\); whereas the normal value for this region is \(Z = 4.314\ \Gamma\).

Having separated out the normal part of the earth’s magnetism, Leyst gives a picture of the anomalous isolines, which shows a very great complexity in the southeastern part of the anomaly, where the ridges branch and form interlacing nest-like centers. The work also gives some numerical material, but the geographical coordinates to which it relates are not indicated at all.

Acad. Lazarev succeeded in organizing geomagnetic observations in this region, most interesting from the geophysical point of view; moreover, for the first time on land the de Colongue instrument and method were applied, giving an accuracy of \(1/4\%\) (in Leyst’s work, \(0.001\)–\(0.002\ N\)).

Despite a number of difficulties of the time through which the expedition was living, Acad. Lazarev, during the reporting period (VII 19–VII 20), succeeded in covering with a network of observations up to 50 square kilometers in the northern region, with about 1,600 points measured.

Ten appended maps at a scale of 16 m/m = 1 kilometer give an idea of the distribution of normal and anomalous geomagnetism according to the observations of 1919–1920.

The maximum value of \(Z\) was observed at \(15.770\ \Gamma\) (later—in winter

in 1920–21 a value close to the maximum observed by Leyst was found).

The important question of the depth at which the magnet-bearing causes lie is touched upon in both works.

Prof. Leyst solves the problem by referring it either to a single pole or to a line of poles and arrives at the following results: the depth at which the pole lies is equal to:

1) the distance between the points where \(z=h\) and \(z=\) maximum,

2) the distance between the points where \(z=h\) and \(h=0\),

3) the distance between the points where \(i=45^\circ\) and \(i=90^\circ\),

or, finally, 4) half the distance between the points where \(h=z\) (or \(i=45^\circ\)).

The depth at which the pole lies is determined by Leyst, on the basis of his observations, to be about 200 meters for the northern region and more than 600 meters for the southern region of the anomaly. Here, incidentally, we note that the borehole sunk at Kochetovka was brought only to 230 meters, and in it, of course, no magnet-bearing masses were discovered.

Acad. Lazarev represents, in the earth, plane-magnetized plates—magnetic sheets with homogeneous magnetization—and gives theoretical considerations for determining the depth of occurrence. It is very interesting to see what results will be yielded by calculations and by the experimental study of models of a magnetized ridge undertaken by Acad. Lazarev at the Scientific Institute.

Leyst gives yet another method for determining the occurrence of the poles—by means of measurements of the gradients in the vertical (downward) direction; at the points of interest analogous measurements must also be made in the upward direction (as was also noted by Lazarev).

Regarding the causes of the anomaly in Kursk province, Prof. Leyst expresses the definite view that only iron ores with a high content of metallic iron can produce anomalies of such intensity.

Only drilling (and deep drilling at that) at well-chosen points can give a decisive and final answer to the question of the cause of the Kursk anomaly. At the same time, during drilling it is possible and necessary to carry out a series of geophysical, geological, and mineralogical observations, and this, of course, will be done.

It is necessary to make use of the work being carried out in the region of the Kursk anomaly for a complete and comprehensive study of this most interesting area. Prof. Leyst had already indicated, from observations in Kursk province, a certain connection between anomalies of terrestrial magnetism and anomalies of the force of gravity; his observations showed (though at a small number of points) that the magnetic anomaly is caused by very dense underground masses. These observations must be repeated on a large scale and with more refined methods; it is also necessary to organize observations of the elements of the atmosphere

…electricity. However, these tasks have already been placed on the agenda by the commission for the study of the Kursk magnetic anomaly, and one may think that the observations will provide interesting material and illuminate the question from a new point of view.

V. Pryanishnikov.