Vol 4 Iss. 3

The well-known, frequently observed phenomenon of coloration of twinned plates that grow through calcite grains along the planes of the first most obtuse rhombohedron (1012) also belongs to the category of pseudochromism phenomena. In this case, the pseudochromism phenomenon is often very striking, and for this reason, as well as because the position of the twinned plates is here easily determined, the phenomenon can be more readily subjected to investigation. This work represents an attempt at such an investigation. The application of the "universal" method to the study greatly supplements the picture of the phenomenon and makes it possible to answer some of the questions it raises. Therefore, I venture to publish the obtained results despite being aware of the incompleteness in the elucidation of the issue.

The question of the accumulation of errors in a mine traverse of arbitrary shape leads to the consideration of complex formulas that do not allow one to draw any general conclusions or provide general rules for resolving the issue in various practical cases. The possibility of simplification begins from the moment we ascribe some regularity to the polygonal line. In ordinary mine traverses, such a simple regularity of the polygonal line is absent; straight extended traverses are encountered rather rarely, and the aforementioned regular polygonal line even more rarely. At the same time, it cannot be said that any regularity whatsoever is absent in the shape of ordinary mine traverses, at least in the coal mines of southern Russia, which we have mainly in mind throughout the entire subsequent discussion.

This article offers an attempt to derive the main principles underlying the application of convergent light, proceeding from the foundations of the theodolite method. This particular approach is the most appropriate if one follows the requirement to proceed from the simpler to the more complex. As will be seen from what follows, the logical development in this direction of the basic provisions of the theodolite method leads to almost the same concepts from which Becke proceeded when explaining the phenomena exhibited by a crystal in convergent light. Apart from some theoretical interest that an exposition of these techniques may have, proceeding from the concepts underlying the theodolite method, it seemed to me useful for the purpose of a comparative assessment of the limits of application of each of these two different methods of research (see the article).

The main obstacle to the development of hardness research has been and remains the fact that there is no certainty in the accuracy of the results obtained, since under different conditions for one and the same substance the results may be different, and thus the possibility of comparing results obtained by different methods is lost. The article describes alloys of lead with tellurium, the process of their preparation, and the methods of research. See the article for the results.

In this brief communication, I shall confine myself to presenting some initial propositions and the principal conclusions of my work (see the article). When considering the thermal state of a piece of solid substance (e.g., a piece of gold), it is therefore necessary to take into account three surfaces: 1. The external surface, which delimits the piece of solid substance from the surrounding space. 2. The internal surface of contact between the crystalline grains constituting the piece. 3. The total internal dynamic (pulsating) surface of the crystalline grains.

The general law referred to here is that a crystal precipitating from a solution tends to assume the smallest surface area. This law, which has a simple and well-known theoretical basis, is usually demonstrated by examples of crystallization, or rather recrystallization, requiring a long time, even months, or at least days. I came across a preparation in which this demonstration can last a few seconds; this preparation is Chilean saltpeter (sodium nitrate), the microscopic crystals of which dissolve from breathing in a few seconds and recrystallize in approximately the same time due to evaporation. Thanks to this rapidity, the aforementioned law is, of course, demonstrated just as quickly.