298 CARNEGIE INSTITUTION OF WASHINGTON. 



this year. Hence, it was decided, on the forthcoming cruise, to equip 

 the atmospheric-electric apparatus aboard the Carnegie with chloride- 

 of-silver batteries. As suppHed to the Carnegie, each battery unit con- 

 sists of 50 cells connected in series. As a precaution against accidental 

 short circuit, each unit also contains a 10,000-ohm resistance coil, 

 while the entire unit is embedded in paraffin as a protection against 

 moisture. Considering our satisfactory experience with this type of 

 cells and the extra precautions observed in mounting them for ship use, 

 it is hoped that their use aboard the Carnegie will constitute a consid- 

 erable improvement. 



Each of the instruments in the atmospheric-electric equipment of 

 the Carnegie was subjected to a thorough overhauling, which in most 

 cases amounted to reconstruction, in the instrument shop. The sugges- 

 tions of the various observers have been carefully considered and, 

 together with the results of general scientific and instrumental progress, 

 have been incorporated where possible in the modifications and repairs 

 which have been made. Various tests and standardizations of the 

 Carnegie's atmospheric-electric instruments have been made. The most 

 important of these have been the calibration, by the Bureau of Stand- 

 ards, of the air-flow meter associated with ion-counter No. 1, and the 

 comparisons in our own laboratory between the air-flow meter of 

 radioactive-content apparatus No. 4 and the Department's standard 

 meter for air-flows of the magnitude involved. The instructions for 

 atmospheric-electric observations aboard the Carnegie were revised 

 and in part rewritten to embody the results of the experience of the 

 last several years and to conform to the various instrumental changes. 

 Earth-current Work. — No experimental work in this subject has been 

 possible during the current year. The activities therein have been 

 limited to critical reports on several papers submitted for publication 

 in Terrestrial Magnetism and Atmospheric Electricity, preparation of 

 letters relating to this subject and the preparation of a ''Note on a 

 Possible Explanation of the 'Electric Tide' Observed at Jersey." This 

 note was published in the same journal for June 1919, and an ab- 

 stract thereof is given on page 316. 



Observatory Work at Washington. — The instrumental equipment and 

 arrangement of the atmospheric-electric observatory on the deck was 

 overhauled and considerably modified in the Department's shop during 

 the latter part of 1918, just prior to the establishment of the Section of 

 Terrestrial Electricity. Since then the operating directions for the 

 observatory have been revised on the basis of experience and instru- 

 mental modifications. Considerable attention has also been given to 

 the development of forms suitable for recording observatory data. 



Both the conductivity and the potential-gradient have been con- 

 tinuously recorded throughout the year, except for an occasional day 

 or part of day when repairs or renovations were needed or under way» 



