Volume 3, Issue 5, 01 November 1932
Index of content:
3(1932); http://dx.doi.org/10.1063/1.1745102View Description Hide Description
Apparatus is developed capable of pushing the magnetostrictive oscillation of nickel to the limit set by its mechanical strength. The intense audible sound produced is introduced under water from beneath the surface, continuous operation of the vibrator being secured by spray cooling. The interiors of corks are charred to cinder by the sound. A fountain 6 cm high forms on the surface of water, and is proved to be due to pumping action of the reciprocating rod and not to radiation pressure.Erosion of metals and of glass by cavitation and resultant water hammer is obtained. Colloids of oil and of carbon in water are produced. Curious fatigue effects in glass are observed. Whitened appearance and erratic motions of air bubbles released in water in the presence of the sound are observed, and theory is developed to explain these and the ``atomization'' of liquids. Flattening of a drop of liquid against a vibrator is observed and attributed to sonic attraction and to the reaction of sonic radiation. Frogs, fish, larvae, and water fleas are killed by the sound. Bacteria are killed so quickly that partial sterilization of milk in continuous process is effected. Striations in a Kundt tube that are parallel to its axis are produced, and an explanatory theory developed.
3(1932); http://dx.doi.org/10.1063/1.1745130View Description Hide Description
At the present time the electromagnetic, electrostatic, Heaviside‐Lorentz, practical and international systems of electric and magnetic units are used side by side in pure and applied electromagnetism. The question is here raised whether the use of this multiplicity of units should continue indefinitely into the future when the conversion tables for translating from any system to any other system show the essential equivalence of all five systems. It is recommended that but one system be legalized and used generally in place of the five systems, and that this universal system be the coherent meter‐kilogram‐second‐ohm or definitive system. It is further recommended that the international ohm be used in this system. This unit is the one actually used in exploring the physical world because laboratory resistances for physics and test room resistances for engineering have been so calibrated. Of far greater importance is the fact that by retaining the international ohm it will be simpler, and completely feasible, to eliminate what Heaviside called ``that unmitigated nuisance, the 4π factor of the present B.A. units'' from our preferred system of units.
A Vacuum Apparatus for Measuring Thermal Expansion at Elevated Temperatures, with Measurements on Platinum, Gold, Magnesium and Zinc3(1932); http://dx.doi.org/10.1063/1.1745131View Description Hide Description
An apparatus for measuring linear thermal expansion between room temperature and 950°C in vacuo by an interference method has been developed and tested on platinum, gold, magnesium and single‐crystal zinc. Although designed primarily for metals which oxidize readily it seems to give excellent results for all metals in the temperature ranges through which their vapor pressure is low. Under conditions such that a metal has a high vapor pressure the performance is not quite so satisfactory because of the deposition of metallic films on some of the cooler parts of the optical train. The refractive index of fused silica for the helium line λ=5877.2 has been calculated for the temperature range 18° to 950°C. A study of the dilatation of single‐crystal zinc yields no evidence for the existence of more than one form between 20° and 350°C.