306 CARNEGIE INSTITUTION OF WASHINGTON. 



for atmospheric electricity, in order to generalize this study on the 

 surface of the globe." 



Unfortunately, in the past, the observations in atmospheric elec- 

 tricity have often been found to be counterfeits of nature because of 

 the errors inherent in the instruments and methods used. Accordingly 

 the much-desired discovery of nature's laws, by "bringing together 

 observation and theory," has not been brought about in the measure 

 desired. None of the proposals for a general electric survey of thf 

 Earth which have been made repeatedly to learned academies, one oe 

 the last having been presented to the International Association of 

 Academies, has been put into effect, doubtless because of the discourag- 

 ing experiences encountered. In spite of the vast work already done 

 by notable investigators, we still have no generally accepted theory 

 of the origin of atmospheric electricity, not even as yet a satisfactory 

 explanation of a thunderstorm. 



Probably one of the most important of recent contributions to the 

 observational data is the summary of observations obtained on the 

 cruises of the Galilee and the Carnegie. A report giving the results 

 up to the end of 1913, obtained by the Department observers and 

 others, was prepared by Dr. Hewlett and published in the September 

 (1914) issue of Terrestrial Magnetism and Atmospheric Electricity. The 

 observations comprised, in addition to the usual meteorological meas- 

 urements, those of the potential gradient, atmospheric conductivity, 

 and radioactive content of the atmosphere. Perhaps the most impor- 

 tant result is a confirmation of the somewhat striking phenomenon 

 that, while the conductivity over the ocean is, on the average, at least 

 as great as over land, the radioactive content is much smaller. The 

 values of the potential gradient obtained at sea were of the same order 

 of magnitude as those on land. (See pp. 324-327). 



INSTRUMENTAL WORK. 



Four new universal magnetic instruments of the type which combines 

 magnetometer and earth inductor, with the accompanying galvanometer, 

 have been designed and constructed in the Department's shop, under 

 Mr. Fleming's superintendence, and have thus far proved very satis- 

 factory. At the end of the year another instrument of this type is 

 under construction ; also one of the type combining magnetometer and 

 theodolite. Other miscellaneous instrumental matters have likewise 

 received attention. 



Some instruments for observations in atmospheric electricity on land 

 and at sea have been constructed under Dr. Swann's direction. 



On April 24-25, the Department took part in the exhibit of instru- 

 ments at the Bureau of Standards in connection with the meeting of 

 the American Physical Society. Several instruments of its own design 

 and make, as well as some new laboratory instruments, were exhibited. 



