SOLAR ECLIPSE OP JANUARY 3, I908 ABBOT 



41 



At about lo'^ 55°^ and ii*^ 45™ the following two series of obser- 

 vations were recorded on the brightness of the center of the sun's 

 crescents visible respectively before and after the eclipse. In each 

 series there Avas employed the "0.077" aperture, and also a series re- 

 sistance of 200 ohms in the galvanometer circuit. The table includes 

 actual readings on the galvanometer scale before and after opening 

 the shutter of the bolometer, sometimes with, sometimes without, the 

 asphaltum screen. In reading the galvanometer, the position of 

 steady condition is first noted ; then the furthest excursion of the 

 spot of light after opening the shutter, which corresponds to the first 

 swing of the galvanometer. In computing actual deflections, no 

 account has been made of drift of zero between the steady position 

 and the end of the first swing, because this interval is only 2 seconds, 

 and the drift was at no time rapid enough to be of import in this 

 brief interval. During all these measurements of sun-brightness the 

 time of swing of the galvanometer was the same as employed during 

 the total eclipse. The places on the sun may be regarded as having 

 been 0.7 radius distant from the center of the solar disk. 



Measurements at io'« SS"* 



