INSTRUMENTS, OBSERVATIONAL PROCEDURE, AND CONSTANTS 



fair weather, the sign of the auxiliary potential was nega- 

 tive. Calibration always was made with the auxiliary 

 potential applied to the inner case, the value of the po- 

 tential being approximately known and assumed to re- 

 main fairly constant. The sensitivity of the electrometer 

 was maintained generally between 10 and 20 volts per 

 scale division on the photographic paper, the tension of 

 newly installed fibers being altered if preliminary cali- 

 brations showed that the desired sensitivity did not exist 

 already. 



Batteries and.Auxiliary Potentials. --Auxiliary po- 

 tentials were used on the inner case of the recording 

 electrometer throughout the cruise. Initially, for the 

 masthead experiments, the auxiliary potential batteries 

 were kept on a shelf in the after galley, and connecting 

 wires were brought up to a marine plug on the starboard 

 rail directly above the galley. From the marine plug, 

 flexible rubber -covered twin cables made the necessary 

 connection to the apparatus. After September 16, 1928, 

 auxiliary potentials were supplied from batteries housed 

 in the small laboratory situated at the forward edge of 

 the quarter-deck on the port side of the cabin compan- 

 ionway. Wires ran beneath the deck from this location 

 to a marine plug on the stern rail. Prior to September 

 16, these batteries supplied auxiliary potentials to the 

 eye-reading apparatus 2, but work with it was discon- 

 tinued at that time. Serious breakdown of insulation in 

 the marine plugs occurred from time to time during the 

 cruise and caused short-circuiting and rapid deteriora- 

 tion of the batteries. 



Insulation Leak. --Under sea conditions, the insula- 

 tion of the amber mountings for the collector rod and 

 for the fibers in the electrometer needed to be tested 

 frequently- -sometimes tests were made two or three 

 times per day, but at least once each day when weather 

 conditions permitted. With the upper part of the collec- 

 tor rod removed, a potential approximating the prevail- 

 ing atmospheric potential was applied to the insulated 

 system of the apparatus by a momentary contact. The 

 deflection of the fibers then was immediately observed 

 and, at the end of a period of four to eight minutes, was 

 observed again. If these readings indicated that the leak 

 exceeded one per cent per minute, the insulation needed 

 to be improved. This rate of leakage was based on the 

 condition that, during regular recording, four collectors 

 were used on the collector rod. With fewer collectors 

 the permissible rate would have been less. When insu- 

 lation had to be improved, the amber insulators were 

 cleaned by applying Putz Pomade with a piece of cham- 

 ois, then later polishing them with a clean piece of 

 chamois. 



Meteorological Observations. --Weather conditions, 

 of vital importance in the interpretation of the atmos- 

 pheric-electric measurements, were carefully record- 

 ed while at sea by the meteorologist for his own rec- 

 ords and by the ship's officers in the ship's log. The 

 meteorological records have been published in Volume 

 I of this series (4), and the ship's log appears both in 

 that volume and in a later section of this one (pp. 47-64). 



Sail Positions and Engine. --Other conditions at sea 

 which affected the measurements, and which had to be re- 

 corded, were the position of the mainsail and the mainsail 

 boom (fig. 18), and the operation of the "main" engine. 

 The boom of the mainsail could be swung into three posi- 

 tionsand the sail itself could be either "set" or "furled." 

 In the ship's record, set and furled were designated as 

 "up" and "down," respectively, and the following 



notations were adopted, for brevity, to indicate the various 

 arrangements: 



MUBS = mainsail up, boom swung out to starboard 

 MUBP = mainsail up, boom swung out to port 

 MDBPC = mainsail down, boom lowered into port crutch 

 MDBS = mainsail down, boom swung out to starboard 

 MDBP = mainsail down, boom swung out to port 



Variations in the amount to which the boom was swung 

 out to starboard or port naturally occurred but, except 

 when the ship was "close-hauled" (and such occasions 

 were recorded) the variations in position were not con- 

 sidered great enough to affect the measurements. The 

 last two arrangements noted above were met with only 

 rarely, and in any case the standardization observa- 

 tions which were made indicated that the sail up or 

 down was of little importance as compared with the 

 position of the boom. The presence of the quarter-deck 

 awning (figs. 18, 19) also was shown, by the standardi- 

 zation observations, to have no appreciable effect on the 

 measurements of potential-gradient, no doubt because 

 the awning was behind the crutch which was in a domi- 

 nant position with respect to the apparatus. 



The operation of the main engine was required to 

 drive the ship in calm weather. The main engine ex- 

 haust was located at the stern and the effect of the at- 

 mospheric pollution produced by the exhaust usually was 

 marked enough to be obvious even in the most casual in- 

 spection of the potential measurements. The operation 

 of the main engine thus made records for certain hours 

 and even whole days of such doubtful value as to make it 

 necessary to discard them. 



Control Program for Potential-Gradient Recorder 



Daily 

 8:00 - 9:00 A.M. Local Mean Time (LMT) 



1. Note positions of electrometer fibers through view- 

 ing window. Correct illumination if not satisfactory. 

 Focus fibers if necessary. 



2. Note whether driving clock is running. 



3. Ground the fibers and note position: position indi- 

 cates whether or not auxiliary is applied to inner 

 case. 



4. Test hourly zero contact by manual closing of hour- 

 ly contact circuit. 



5. Change drying material on electrometer if neces- 

 sary. 



6. Remove collectors and make leak test for approxi- 

 mately five minutes, noting movement of fibers 

 through viewing window during this interval. If leak 

 exceeds one per cent per minute (rate based on use 

 of four collectors during regular recording), im- 

 prove the insulation. 



7. On a "Daily Record" form record times of above 

 observations and results obtained. 



Greenwich Mean Noon (or Midnight) 



1. Advance photographic paper 5 cm. 



2. Note position of electrometer fibers through viewing 

 window. 



3. Make appropriate notes on daily record. 

 5:00-6:00 P.M. LMT 



Repeat items 1 to 7 under 8:00 - 9:00 A.M. above. 



Weekly 



1. Calibrate recorder over voltage range of zero to ap- 

 proximately 300 volts, then allow to record for fif- 

 teen minutes. 



2. Roll balance of photographic paper onto bottom roller 

 in recorder box. 



