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The Atmospheric Obscurity of x912-13. J. MAURER and C. DORNO. (Meteorolog. Zeitschr., xxxi, 49.)--At the beginning of 19i 3 the president of the Radiation Commission of the International Meteorological Committee, J. Maurer, issued a circular letter to meteorological institutes, asking that observational material on the remarkable atmospheric obscurity of 1912 should be sent to him. The paper is a report on the results obtained on working up the material received in response to the letter.
The general cause of the obscurity is attributed to the volcanic eruption of Katmai, in Alaska, on June 6, 1912 ; for successive phases of obscurity can be traced from place to place in relation to the time which had elapsed since the eruption. The first phase began on June 6 in the form of high, clear clouds which travelled from WNW. to ESE. This phase reached Z~irieh on June 23rd, Egypt on June 28th, and it was not sufficiently intense to affect the records of Campbell-Stokes sunshine recorders. The maximum intensity of this phase at any place usually occurred at one to three weeks after the commencement. The second phase, which was similar in character to the first, was observed on Mount Wilson on June 2ISt. It reached Algiers on July I Ith and Egypt on August 8th. The third phase was noted in Washington to commence from July I9th to 26th, and it arrived in Egypt at the end of August, but this phase was lacking altogether at some stations, while at others the maximum of disturbance occurred during its course. The fourth phase spread from America to Egypt during the month of September. The end of the disturbance was noted in October at most places. The phenomena appeared to be confined to that part of the northern hemisphere lying between the polar circle and the Tropic of Cancer, but it is not ascertained whether they extended completely round the globe, within those limits.
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