An air-base stereoscope

Three magnifying stereoscopes, intended for orienting stereo pairs of vertical air photographs and then ruling in the directions of the projections of the air bases on the photographs, were designed and constructed in the National Research Laboratories for the Department of Mines and Resources. Some features found useful in previously designed photogrammetric instruments were incorporated.

The mechanism of the hydrogen-oxygen reaction; the reaction in vessels coated with alkali iodides

Previous work on the hydrogen-oxygen combination in vessels coated with alkali halides showed that with the iodides the temperature dependence of the reaction rate is abnormal. In iodide-coated vessels the whole mechanism of the reaction is now shown to be different: the greatly reduced rate is independent of [H 2 ], proportional to a + b [O 2 ] and independent of added nitrogen, all in sharp contrast with what is found in chloride-coated vessels. The normal reaction is thought to be completely suppressed by minute amounts of iodine liber­ated into the gas phase, a residual surface reaction being measured. The chemical actions which must be assumed to occur between the iodide and the gases provide indirect evidence for the probable mode of operation of the other halide salts in controlling the hydrogen-oxygen combination.