A new stroboscopic device with strong illumination

woultl IX set free. Decinormal silver nitrate was mixed with citaril? _;olution and sodium hydroxide of similar strength, heatetl for thirt! The l)reminutes on the water-bath and allowed to stand overnight. cipitate was collected on a suitable filter, washed and dried (at from TIO0 to 120’). A similar method was applied to gold chloride solu-The test analyses submitted show very satisfactory data. tion. Ksperiments with bismuth have so far not yielded useful results. I-I. I_. L. and A New Stroboscopic Device with Strong Illumination. A. SEGUIX. (Comptcs Readus, Oct. 26, 1()25.)-h long ago as 1873 Crova knew the use of a Geissler tube for the production of \Vith either a vibratintermittent illumination at controlled intervals. ing or a rotating interrupter, the arc formed by breaking the current limited the strength of the current in the primary, and consequently in the secondary coil also, so that the available current through the tube produced but feeble flashes of light. To avoid this hampering dependence of the intensity of light upon the current capacity of the interrupter, in the new apparatus the illumination comes from the discharge of a strong battery of condensers through a neon tube. This discharge cannot pass by its own voltage but must wait to be set off by an induced current due to the interruption of a current by the timing device. Th e intensity of the momentarv illumination It can In addition be can, therefore, be made as great as is desired. caused to be practically instantaneous. In one case two marks, one mm. apart, could be clearly seen on a disc, illuminated by this device, even when it was rotating so that its periphery had a speed of IOO mm. per sec. The strong intensity of the flashes of light produced in the tube is of value in studying the motion and vibration of large and somewhat inaccessible machinery. G. F. s. The Thirteen-month Calendar. (U. S. Department of Agriculture, Clip Sheet, No. 397, Feb. I, r926.)-Fresh stimulus has recently been given to the reform of the calendar by the action of the committee of inquiry of the League of Nations in calling representatives of the Roman, Greek, and other orthodox churches of the East, the Anglican Church of Great Britain, and about 100 Protestant churches to discuss the advisability of making Easter a fixed instead of a movable date, dependent on the full moon. The first or second Sunday in April has been suggested. Further sessions of the committee of inquiry are to be held soon to make definite recommendations to the League of Xations regarcling plans for calendar reform. Enthusiastic support has been given in many quarters to the plan that would divide the year into thirteen twenty-eight-day months, with an extra day at the end of the last week in December. Every four years a leap-year day would be inserted at the end of June. The change, it is said, could be made easily on January I, 1928, as that will be Sunday. Prof. C. F. Marvin, Chief of the U. S. 1Veather Bureau, indorses