WEATHEK BUKEAU. 267 



Mount Weather Bulletin. — The Bulletin of the Mount Weather 

 Observatory has continued to publish the results of the important 

 work done at that station. Its last volume, with index, completed 

 en June 15, 1912, includes four regular quarterly parts and two extra 

 parts, of which No. 4, the " balloon number," gives a complete sum- 

 mary of all work done during 1904-1911 in the United States with 

 sounding balloons. This volume also includes a summary by Dr. 

 Blair of all the daily kite flights during the three years July 1, 1907, 

 to June 30, 1910. In addition to these extensive summaries of re- 

 sults by flights from kites and balloons the Bulletin has included 

 several special memoirs by Profs. Henry, Humphreys, and Kimball. 

 Prof. A. C. Orehore and Capt. G. O. Squier, of the Army Signal 

 Office, have contributed a paper on the recording of minute changes 

 of pressure by a special form of barograph. The bureau is indebted 

 to the kindness of Mr. J. W. Sandstrom for the memoir published 

 in the Bulletin, Volume III, part 6, "The relation between atmos- 

 pheric pressure and wind," which has attracted wide attention. A 

 second memoir, dealing specifically with the wind phenomena of 

 mountains and seacoast, has been prepared by the same authority 

 and will appear in full in the next volume of the Bulletin. The 

 remarkable success attending Prof. Stoermer's study of the aurora 

 borealis was fully explained m the third volume of the Bulletin. His 

 complete report as now published shows that this subject must be 

 taken up by his methods and by American observers if we would con- 

 tribute to our knowledge of atmospheric electricity over the Western 

 Hemisphere. Of the original contributions to the science and litera- 

 ture of meteorology made during the year by Prof. W. J. Huni- 

 phreys, of the scientific staff of the Weather Bureau, several discuss 

 the physical interpretation of certain luminous and other phenomena 

 of the upper atmosphere. One paper, "Holes in the air," is of 

 special interest to aviators, since it discusses in some detail a number 

 of distinct atmospheric conditions that render flying dangerous, and 

 also shows when and where they are most likely to occur and how 

 best to avoid them. Another paper discusses at length one of the 

 most difficult problems of meteorology — the phenomenon of the 12- 

 hour periodic variation of the barometer. It is believed that the con- 

 tributing causes of this phenomenon, of which there seem to be at 

 least three, have been found and that this " meteorological mystery," 

 as it has been termed, is at last substantially solved. 



SCHOOL OF INSTRUCTION. 



The duties of assistant observer at the 200 stations of the weather 

 service outside of Wiishington are largely technical in character, 

 and require on the part of the employee a knowledge of instruments 

 and of methods of tabulating the results therefrom that can be ob- 

 tained only by actual experience. It may be safely said that a new 

 employee does not become really useful until he has had at least 

 three months' experience under the guidance of a trained observer. 

 If he is given immediate station assignment, the quality of the in- 

 struction that he will receive will depend largely on the kind of work 

 performed at his station. Certain classes of work, such as the making 

 of weather maps and the taking of observations, are common to all 



