Crushing cubes with different sides did not indicate any dependence of the time resistance on size: experiments 21,3 gave

The results of determinations of resistance to fracture are expressed by the following table:

Determinations of density gave the same results as in previous years.

K. B. Weinberg.

Magnetic Declination in Siberia in the Seventeenth and Eighteenth Centuries (author’s abstract).

In addition to the 20 direct observations collected by Hansteen and given in the compilation of B. P. Weinberg (Izv. Instituta issl. Sib., 1, 2, 1920), I used Remezov’s maps, in which the directions of the cardinal points are indicated by the magnetic needle (by comparison of the directions of rivers), the map of Peter Godunov, and the orientation of the Alekseevsky Monastery in Tomsk, placed, apparently, with its altar to the east along the magnetic meridian. In the table below are given: the number according to the compilation, the locality, the values of declination for 1910 and 1829 (from the same compilation) and in 1600 (from Hansteen’s map, in Neumayer’s atlas); the figures in parentheses denote the declination computed according to the formula:

\[ \delta = -3^\circ .26 + 0.03|\varphi - 55^\circ| + 0.15|\lambda - 80^\circ| - \]
\[ - (0.11 - 2.5\cdot 10^{-3}|\lambda - 75^\circ| + 3.3\cdot 10^{-3}|\varphi - 55^\circ|)(t - 1760) + \]
\[ + 1.5\cdot 10^{-4}(t - 1760)^2 - 1.0\sin 0.021(t - 1760). \]

This formula expresses the values of declination for 1910 and 1829 with a mean error of ±1°.1, for 1805—1716—±1°.4; 1685—60—±5°.3 and 1600—±1°.3. These errors correspond to deviations from the sche-

¹) Weathered specimens.

of the mathematical formula and the inaccuracies in determining the values of declination over 1–2 centuries from maps and from the orientation of churches, and therefore make it desirable to determine the orientation of other ancient churches of Siberia and Russia.