Inauguration of Atmospheric-Electric Observations 363 



much assistance in the organization of the work, both by advice and by personal 

 help in the training of two of the first observers. 



Furthermore, during a special trip to Europe in the spring of 1905, the Direc- 

 tor received most valuable aid and counsel regarding atmospheric-electric work 

 from Professors von Bezold, Chree, Ebert, Mascart, Schuster, Shaw, Rucker, and 

 Wiechert, as also again from Professors Elster and Geitel. 



The need in atmospheric electricity of a general series of accurate observations 

 over as large a portion of the Earth's surface as possible may perhaps have been 

 first definitely set forth by the late Professor Rowland in his address before the 

 Congress of Electricians, held at Paris, September 1881. A general electric survey 

 of the ocean areas possesses pecuUar advantages over that of land areas, not merely 

 because of the greatly preponderating extent of area, but because of the freedom 

 from the disturbing influences of topographic and cultural features. 



To reap the full benefit of this latter advantage, however, it is essential to 

 eliminate as far as possible the disturbing influences caused by the vessel, itself, 

 on which the observations are made. In brief, the difficulties to be overcome, both 

 of an instrumental nature and of an observational nature, are such that it was not 

 deemed wise to undertake atmospheric-electric work on the oceans until some of the 

 problems of accurate ocean magnetic work had been solved. 



It may be recalled also that the types of instruments used in atmospheric- 

 electric work ten years ago were the subject of frequent criticism and changes. 

 Before an instrument had been completed by a European maker, it had been 

 modified or superseded by some other instrument. Accordingly, it was not until 

 the middle of the third and final cruise of the Galilee, namely, in August 1907, that 

 our ocean measurements of the electrical elements of the atmosphere could be 

 undertaken, and then only in a preUminary manner. The work was continued 

 tentatively on the first and second cruises of the Carnegie, 1909-1913. 



When the laboratory (PI. 21) of the Department of Terrestrial Magnetism at 

 Washington was completed in 1914, the requisite facilities became available for 

 experimental and theoretical studies of the various atmospheric-electric instruments 

 and methods of observation. As the result, certain modifications in existing types 

 of instruments could be made, and new types and methods devised, which will be 

 described later. When, therefore, the Carnegie set out on her fourth cruise from 

 New York in INIarch 1915, the work in atmospheric electricity could be undertaken 

 with greater hope of successful accompUshment than theretofore possible. 



The main observations and results for the various cruises, as based on the 

 observers' reports, are first set forth separately in the foUowing pages. The results 

 for the Carnegie's fourth cruise wiU be found given in full; they have been compiled 

 and discussed by W. F. G. Swann, who, in the computational work, has been assisted 

 by S. J. Mauchly and D. M. Wise. The discussion includes a comparison of the 

 results with land values, and with former ocean values obtained by the Department 

 of Terrestrial Magnetism and others. In conclusion, special reference should be 

 made to effective aid rendered by those whose names do not appear specifically 

 elsewhere: J. A. Fleming, J. A. Widraer, and C. A. Kotterman. 



