By G. W. Vinal and L. M. Ritchie. [ABSTRACT]
THIS apparatus has been devised to meet the needs of the Bureau of Standards in making tests of dry cells and storage batteries, but is applicable to nearly any form of intermittent testing requiring the closing of electrical circuits at regular time intervals. The particular advantages of this type of apparatus for making these tests are : (I ) e 1imination of rapidly-moving parts; (2) accuracy of the time intervals; (3) possibility of making a number of different tests simultaneously with the same apparatus. RELATIVE
ATMOSPHERE: By Dr. E. Karrer and E. P. Tyndall. [ABSTRACT]
on the transmission of light by the atmosphere are essential in order to compare various searchlight beams whose characteristics are invariably obtained at different times and under different atmospheric conditions ; and are also ess’ential in all considerations as to what the color of a searchlight beam For these latter considerations should be to obtain best results. the relative spectral transmission of the atmosphere is required. Not only are such data on the spectral transmission of the atmosphere of value to the theory and practice of searchlight illumination but are also of prime importance to an intelligent consideration of headlamps for automobiles, and locomotives, as well as to the selection and development of color schemes and emulsions for use in aerial photography. The method consisted in comparing, wave length for wave length, the intensity of a ray of light emitted by an incandescent lamp, after reflection from a mirror 600 rnp distait with that of a ray directly entering the spectrophotometer near the lamp. Either of these rays could be allowed to enter one of the collimators of a Brace spectrophotometer, to be compared alternately 4Technologic Paper No. 171. ‘Scientific Paper No. $39.