130 



OCEAN ATMOSPHERIC -ELECTRIC RESULTS 



Table 2. Reduction factor observations for potential-gradient, Atlantic Ocean, Carnegie cruise VII 



Stern potential-gradient apparatus no. 2 



Date 



GMT 



Begin 



End 



Potential-gradient 

 eye reading 



Land 



Ship's 

 stern 



Reduction factor for 

 ship's stern eye reading 



MUBP 



MDBPC 



MDBP 



Remarks 



3.13 

 3.19 

 3.02 

 3.51 



Eye electrometer no. 25 on 



shore 

 Recorder 4946 on shore 

 Eye electrometer no 28 at 



stern in apparatus no. 2 



3.21 



Mean MUBP-MDBP = 3.28 



Table 3. Reduction-factor observations for potential-gradient, Atlantic Ocean, Carnepe cruise VH 

 Potential-gradient apparatus no. 2 and recorder 4946 at stern 



Date 



GMT 



Begin 



End 



Potential-gradient 



Land 

 eye 

 read- 

 ing 



Ship's 

 stern 

 eye 

 read- 

 ing 



Ship's 

 stern 

 re- 

 cord- 

 er 



Reduction factor for 

 ship's stern eye reading 



Reduction factor for 

 ship's stern recorder 



MUBP MUBS MDBPC 



MUBP MUBS MDBPC 



1928 



July 25 



25 



25 



25 



h m 



12 27 



13 09 



14 25 



15 05 



h m 



12 55 



13 55 



14 55 



15 55 



V/m 



139.2 

 155.6 

 158.9 

 171.5 



Volts 



60.7 

 77.4 

 60.2 

 79.1 



Volts 



266 

 256 

 292 



2.17 



2.29 

 2.01 



2.64 



0.59 



0.59 



0.62 



Means 



2.17 



2.15 



2.64 



0.59 



0.59 



0.62 



Eye electrometer no. 26 on shore. Eye electrometer no. 28 at stern. Ship's draft 11.5 ft. for'd, 

 13.85 ft. aft. Installed ship's recorder at stern at Hamburg, July 7, 1928, with bent-arm collector rod. 

 Ship anchored one -half mile from shore station. 



and increased through later observations, the conditions 

 at the two stations evidently became more alike. The 

 twelve acceptable sets are shown in table 2, where the 

 values of volts per meter for the shore station are those 

 obtaino i with the eye-reading electrometer rather than 

 the recorder. The recorder results will not be shown in 

 tabular form as they merely repeat the results in table 2. 



For previous cruises of the Carnegie the reduction 

 factor fo- MUBP or MUBS was 2.85 and for MDBPC, 

 3.77. In table 2 the comparable figures are 3.28 and 

 3.96, respectively, which are some 5 to 15 per cent 

 larger. These increased values are accepted as reason- 

 able. 



Series 2, made at Iceland with the recorder in- 

 stalled on the stern rail near the eye-reading apparatus, 

 gave results for the eye-reading apparatus which are 

 low in comparison with those of series 1. They are al- 

 most exactly two-thirds of the Kitts Point values for 

 comparable sail positions. For the recorder the factors 

 are approximately 0.6 for all sail positions, which ap- 

 pears to be reasonable. The results for series 2 are 

 shown in table 3 . 



It is unlikely that the installation of the recorder on 

 the stern rail produced the decrease in the factors for 



the eye-reading apparatus. The bent collector rod, 

 being at air potential, would not distort the field, and the 

 recorder box was too small to introduce any consider- 

 able distortion in view of the dominant position of the 

 boom crutch and lifeboat. That the weather was respon- 

 sible also seems unlikely. The weather was not partic- 

 ularly favorable, and cloudiness increased throughout 

 the five hours of observation until rain fell in the last 

 hour, but if the weather had been responsible, the effect 

 should have been the same on the stern recorder as on 

 the eye-reading apparatus, and this was not the case. 

 The possible existence of instrumental defects or diffi- 

 culties was recognized; the eye-reading data were care- 

 fully examined with this in mind, but nothing was found 

 that would explain the low factors. It was noted, how- 

 ever, that if the measured volts for both the recorder 

 and the eye-reading apparatus were to be reduced in all 

 cases by an amount of 20 to 25 volts, the factors for the 

 eye -reading apparatus would be increased about 50 per 

 cent to agree with those obtained at Kitts Point and for 

 the recorder would be increased about 10 per cent to 

 agree with those obtained later in series 3 at Barbados. 

 Why both stern instruments would give values 20 to 25 

 volts too high is difficult to explain. In any case, the low 



