42 



OCEAN ATMOSPHERIC -ELECTRIC RESULTS 



to ensure that the value of temperature entered in the 

 records approximates the mean value for the interval 

 occupied by the observation. The chief source of uncer- 

 tainty in comparisons of 5503 with 1 is the difficulty in 

 obtaining with 5503 an accurate reading of fibers so widely 

 separated, when, because of the ship's motion, both are 

 moving irregularly. Taking this into accoimt, and 

 also the temperature effect already noted, the compari- 

 sons, so far, may be considered to be satisfactory. 

 Further sets will be obtained as frequently as condi- 

 tions permit. 



In order to avoid the risks involved in moving the 

 penetrating radiation apparatus 5503 during magnetic 

 observations in the after dome, tests were made at the 

 Apia Observatory to determine the magnetic effect of 

 the instrument. The distance between penetrating appa- 

 ratus 5503 and the marine deflector in the after dome is 

 3.5 meters. With magnetometer 12 mounted on the ob- 

 servatory pier, the deflection produced on the freely 

 suspended magnet by the approach of 5503 was: 



Distance, 

 meters 



Deflection 



Scale divisions Minutes 



3.5 

 3.0 

 2.5 

 2.0 



0.0 

 0.0 

 0.1 

 1.0 



0.0 

 0.0 

 0.2 

 2.0 



These data indicate that no Important disturbance is 

 caused by the presence of penetrating radiation appara- 

 tus 5503 even as near as 2.5 meters. It will be unnec- 

 essary, therefore, to move the instrument in the future 

 during the magnetic program. 



The sodium in the drying tubes of penetrating radi- 

 ation apparatus 1 was renewed on June 2, We have only 

 two spare glass drying tubes for this apparatus. This 

 is just the number required to make a rapid renewal of 

 drying material and it seems desirable that we should 

 have a reserve stock in case of damage. 



On June 3 an attempt was made to eliminate the 

 "flicker" or sudden movement in the fiber of penetrat- 

 ing radiation apparatus 1 which had been evident, though 

 not serious, for the few days preceding. It probably was 

 caused by a defective cell or cells in one of the plate 

 batteries, though no such defect could be located in test- 

 ing the batteries with the voltmeter. The megohm re- 

 sistor in the battery circuit was changed, and finally 

 both silver chloride batteries were replaced by four 

 Burgess "B" batteries, after which the fiber behaved 

 quite normally. It will be interesting to see how long 

 these batteries remain efficient for this service. 



Nuclei Counter 5. - -Observations have been made 

 with this instrument at every opportunity. When near 

 the end of the diurnal -variation run of April 30 and May 

 1, the observer fell, causing the instrument to fall also, 

 breaking the pump stem at the soldered joint at the top 

 of the pump cylinder, and shattering the mirror reflec- 

 tor. The stem was resoldered successfully the same 



day and the reflector repaired, so that observations 

 could be made as usual the following day. 



Values rather larger than ordinarily obtained thus 

 far were encountered on May 17 and 18, just before 

 reaching Guam and again on May 27 and 28. On the lat- 

 ter date the vessel was about 100 miles to leeward of 

 the northern Marianas group, which is marked on the 

 chart as volcanic. On May 18 an attempt was made to 

 preserve a sample of the nuclear material by placing a 

 microscope slide, smeared with balsam, on the wire 

 screen of the conductivity apparatus air tube and run- 

 ning the fan for fifteen minutes. This sample wastrans- 

 mitted to Washington for examination. 



Silver Chloride Batteries. --Soon after leaving Apia 

 the whole stock of silver chloride batteries was tested 

 and the entire supply of 280 cells received at Callaowas 

 used in making replacements. We have now, besides the 

 batteries on service in the shelf cupboards below the 

 instruments (five batteries in all), two complete 100-cell 

 units and 80 cells of another which show high enough 

 voltage to be called in good condition. The Burgess and 

 Eveready "B" batteries used for potential gradient aux- 

 iliary potential and leak tests and those used for charg- 

 ing penetrating radiation apparatus 5503 appear to be 

 holding up remarkably well. 



Comme nt s 



Change of Sensitivitv of Potential-Gradient Record- 

 er. --The proposals for obtaining closer check of the 

 sensitivity of the potential-gradient recorder should be 

 helpful. When the change is owing to some alteration in 

 the auxiliary potential, such as is inferred to have oc- 

 curred at Guam, then a comparison of the hourly zeros 

 should make this manifest, and an exact correction 

 could be made if the recorder is calibrated with inner 

 case earthed. Of course if the tension on the fibers has 

 changed, the correction would require a knowledge of 

 the value of the auxiliary potential. If the latter re- 

 mained constant, then the change in sensitivity could be 

 determined from a comparison of the hourly zero de- 

 flections. 



Comparison of Penetrating Radiation Apparatuses. 

 --The careful observations for comparing penetrating 

 radiation apparatus 1 and penetrating radiation appara- 

 tus 5503 and the analyses of these observations have 

 been studied. Apparatus 5503 is definitely subject to 

 more variation than is no. 1, and, furthermore, those 

 variations unmistakably are of instrumental origin. 

 They seem to be associated with the temperature of the 

 Instrument but it is not evident how temperature should 

 give rise to such changes. It may be necessary to re- 

 place 5503 by its companion instrument 5658 when the 

 Carnegie arrives at San Francisco. 



Nuclei Counter 5. --The accident which befell this 

 instrument is unfortunate. This calls to attention the 

 need of a reserve counter on the Carnegie . According- 

 ly it is being recommended that counter 2 be sent to the 

 Carnegie at San Francisco. 



