CAPE EVANS, SERIES B, 1911. 



This series of observations was made on August 16th, 17th and 18th in the same 

 ice cave as Series A, but with improvements of the apparatus in certain details. 



Time observations. For these observations the oil lamp of the old fixed mark was 

 replaced by a small 4- volt incandescent lamp, screwed to the front of the same post as 

 was previously used, and actuated by a set of dry cells kept in an (heat) insulated box. 

 This gave a much more regular light for the " fixed mark " and could not be blown out 

 by the wind. 



The transit instrument was improved by the simple device of soldering the eyepiece 

 in place, together with the sliding tube for focussing. The level remained unchanged 

 with a rubber cork in each end. 



Pendulum apparatus. For the better reading of the temperature in the dummy 

 pendulum, an iron rod \ inch in diameter was frozen solidly into the shelf of ice in front 

 of the pendulum stand and on it was fixed the microscope from a Wilson Portable 

 Electroscope,* for reading the temperature more accurately. Thermometer No. 41204 

 was used in Series B. 



In this series and in all observations after this date, the heavy brass disc on which 

 the dummy pendulum rested was replaced by one of cork, in order that the tempera- 

 ture of the dummy might the more nearly approach the temperature of the pendulums 

 themselves. These were of course hanging freely from the agate planes and nob in 

 any way in metallic connection with the stand. 



Rate of Clock " S.C." Star observations were made in the same manner as in 

 Series A, but with somewhat better results. A similar method of reduction was used 

 by Mr. Curtis as in the first series of observations. A value of the azimuth constant was 

 determined for each day's observations (collimation neglected), the mean taken as the 

 true azimuth, the sights recalculated and the collimation correction applied. 



The azimuth constant deduced from the different days of observation gave on 



Aug. 15th .. .. 7-2 sec. July 30th .. .. 10-4 sec. 



16th .. 9-1 Aug. 1st .. 10-0 



17th 9-0 2nd .. 10-2 



18th .. 10-5 ,., 7th .. 14-3 



8th 8-7 



As in the preceding series, the azimuth has been taken as +10*0 sec. throughout. 

 * Kindly lent by the Cambridge Scientific Instrument Co. 



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