REPORT ON ATMOSPHERIC ELECTRIC WORK 



33 



the soft grade) and perhaps, more conveniently, shellac 

 and alcohol may be used for recementing. The shel- 

 lac should be thoroughly dry and all excess of alco- 

 hol removed before the instrument Is reassembled. 

 Naturally every care must be used to avoid salt particles 

 being inclosed in the chamber and the air inclosed must 



be as dry as possible. Even though the residual ioniza- 

 tion will douMless have changed, this can l>e measured 

 later. The other instrument to be supi)lied by Gunther 

 and Tegetmeyer will be sent as soon as possible to re- 

 place 5503, which should then be returned to Washing- 

 ton unless otherwise directed. 



REYKJAVIK, ICELAND TO BARBADOS, B. W. I., JULY 27 TO SEPTEMBER 16, 1928 



General . --Observations of the atmospheric-electric 

 elements have been made practically daily throughout 

 this leg of the cruise. Low values of ionic content and 

 conductivity were obtained until reaching 13° north lati- 

 tude on August 27. From August 27 to September 3 the 

 values obtained were higher than normal and as the 

 westerly course to Barbados was begun the values grad- 

 ually became normal. On six occasions complete 24- 

 hour diurnal-variation runs were obtained and on three 

 other days diurnal -variation observations were begun 

 but had to be discontinued because of bad weather. 



Potential-Gradient Recorder . --Various difficulties 

 have been encountered in obtaining good scalable traces. 

 The cMef difficulty has been the instability of the fibers 

 of the electrometer. Part of this (and the greater part) 

 is electrical, but there is some mechanical shifting of 

 the fibers with the pitch and roll of the ship and, at 

 times of light wind, with flapping of the mainsail and 

 movement of the boom. An effort to reduce the electri- 

 cal activity of the fibers was made by removing three of 

 the four ionium discs from the collector system. With 

 tills arrangement, however, the electrometer deflection 

 took several minutes to come up to its normal value af- 

 ter each hourly zero and so the discs were replaced. 

 Various sensitivities have been tried and the one now 

 being used (about 25 volts per division for each fiber) 

 seems the most suitable. An inspection of the spare 

 sets of fibers supplied showed that there were some on 

 which the gold sputtering had flaked badly. When one 

 box was opened, all three fiber systems were found 

 broken. One set of fibers was broken by an observer 

 when he mounted them in the recorder, during consider- 

 able motion of the ship, in place of a set of which the 

 fibers were too fine to use at the required sensitivity. 

 For these reasons, a request was made that more fibers 

 be sent to Balix)a. It appears that thicker fibers should 

 be supplied as they will give a more satisfactory trace 

 in addition to the fact that the added inertia will tend to 

 damp out some of the larger fluctuations. Control ob- 

 servations with potential- gradient apparatus 2 have been 

 made almost daily but it will be seen from the traces 

 that, owing to the raising and lowering of the umbrella, 

 the trace during the observation assumes a character 

 different from that preceding and following. For this 

 reason it seems hardly worth while to try to standardize 

 the recorder by observations at the stern but rather to 

 do it by land comparisons, using another recorder on 

 shore over a period of several days, as we plan to do at 

 Barbados. Another source of trouble which occasioned 

 some loss of trace was the loosening of the objective 

 lens inside the tube connecting the electrometer to the 

 recording-paper housing. This lens fits against a spi- 

 ral spring in the inner case of the electrometer and, 

 presumably from some continuous motion, it worked 

 loose, thus throwing the trace out of focus. Several 

 attempts to refocus by the ordinary method were made 

 before the real cause of the trouble was discovered. 



After the lens was replaced it would remain in position 

 only for about two days. Finally, on Septeml)er 10, the 

 lens mounting was fixed in the tul>e with sheUac and no 

 further trouble has been experienced up to date. 



Potential-Gradient Apparatus 2. --The sulphur in- 

 sulators for this have had to be recast since leaving 

 Reykjavik, thus reducing insulation difficulties, but 

 considerable trouble has been experienced with the hard 

 rubber insulator near the handle of the rod supporting 

 the umbrella- shaped conductor. It seems necessary to 

 have this unscrewed about one -half turn before it acts 

 as an Insulator. A brass cover was made for this insu- 

 lator and was found quite effective in use. 



Penetrating Radiation Apparatus Gunther and Teget - 

 meyer 5503. --Inspection of the values of R obtained 

 after about August 9 and also the attempted calibration 

 of August 19 show that the deflection of the fibers is not 

 representative of the applied voltages. The cause is not 

 definitely known but the fact can be ascribed only to some 

 defect in the fiber system itself. It has been the prac- 

 tice, during the magnetic observations in the after dome, 

 to remove the penetrating radiation instrument to the 

 photographic dark room, but the greatest care has been 

 exercised in the removal at all times and it is certain 

 that the instrument has suffered no sudden jar. When in 

 the atmospheric-electric house, the instrument is se- 

 cured by a leather strap to the port bench, between the 

 radioactive-content electrometer and penetrating radia- 

 tion apparatus 1. It is hoped that some satisfactory 

 remedy can be suggested for the difficulty here men- 

 tioned as the comparisons between this Instrument and 

 the older one were proving to be quite good. 



Penetrating Radiation Apparatus l. --This instru- 

 ment has performed very well and some instructive di- 

 urnal-variation curves have been obtained. In this 

 connection attention is drawn to the form now being used 

 for this work. The old form is not very suitable for con- 

 tinued observation and it is suggested that some forms 

 might be supplied to obviate the work of ruling them up 

 here. It wUl be noticed that the values in general are lower 

 than those obtained on previous cruises. This change pos- 

 sibly may be owing to the fact that formerly a part of the 

 roof over the chamber was removed during observation. 

 This seems a good proof of the desirability of a second 

 instrument such as the Kolhorster, with which observa- 

 tions could be made out-of-doors as suggested in Mr. 

 Gish's memorandum of July 7, which was acknowledged 

 in our last report. It was necessary to renew the sodium 

 in the drying tubes on September 13, the operation being 

 performed with as little exposure of the orifices as pos- 

 sible, as suggested in Mr. Gish's memorandum. 



Radioactive Content Apparatus. - -Several attempts 

 have been made to maintain a high potential on the col- 

 lecting system but with the same negative results as 

 previously reported. There has been too great pressure 

 of work in other lines to warrant further effort to obtain 

 results with this instrument. 



