Volume 3, Issue 6, 01 December 1932
Index of content:
3(1932); http://dx.doi.org/10.1063/1.1745133View Description Hide Description
The theory of the interpretation of seismic travel‐time curves for refracted rays in horizontal structures is treated after the manner of Herglotz‐Wiechert, under the customary assumption that the ray paths obey the laws of geometrical optics. Multiple valued travel‐time curves, discontinuous velocity functions, and the discontinuous travel‐time curves associated with a slower speed bed receive special consideration. It appears that interpretations satisfactory from the theoretical point of view may be obtained in these cases, although, experimentally, sufficiently complete data to meet the requirements of theory may often be difficult or impossible to obtain.
3(1932); http://dx.doi.org/10.1063/1.1745134View Description Hide Description
In this paper is discussed the problem of measurement of the small, but not always negligible, phase angles of resistors, with special reference to shielded resistors of 1000 ohms and above. Several types of shielded resistors are described briefly, among which is the ideally shielded, low‐phase‐angle resistor, recently constructed by the writer. The substitution method developed is one in which the resistor, the phase angle of which is desired, is compared, by means of bridge circuit, to a reference standard of a simple geometric configuration and of approximately the same resistance as that of the resistor. The results of measurements, at frequencies of 500 and 60 cycles, on three ideally shielded resistors are given. By a series connection of resistors it is possible to extend the range of the method to 50,000 ohms.
3(1932); http://dx.doi.org/10.1063/1.1745136View Description Hide Description
The capillary rise of oil in vertical strips of impregnated paper obeys the same law as the rise of liquids in capillary tubes of circular cross section. From the viscosity and surface tension of an oil and its rate of rise in a given paper, it is possible to compute the ``effective capillary radius'' of the capillary pores of the paper. The rate of rise in a calibrated paper affords a convenient means of measuring the surface tension when the viscosity of the liquid is known. The rate of penetration of an oil into a paper is directly proportional to the ``penetrativity'' of the oil as defined in the theory of capillary action. The penetrativities of nine insulating oils and the effective capillary radii of seven different papers have been determined. A uniform relationship between the effective capillary radius and the Gurley air resistance of the paper is indicated.