86 PROCEEDINGS OF THE AMERICAN ACADEMY. 



be considered rough. Such a change in the intensity of the earth's 

 field as might come from a passing train of electric cars at two hundred 

 yards distance would appreciably affect the first value given. 



The results of this computation are respectively 161, 188, 163, 157, 

 174, 173, 171, 178. So far as one may judge from these and from sim- 

 ilar sets obtained with other systems there is no very strong evidence 

 that I changes materially with T, unless it be for extreme values. The 

 damping coefficient is by no means constant, for its value increases 

 rapidly with the restoring force but not according to any easily recog- 

 nizable law. 



VIII. In the next series of experiments with the apparatus repre- 

 sented in Figure 6 Q' was displaced by another small bar magnet 6.0 

 centimeters long which, when placed perpendicular to the earth's field 

 at room temperature, had a magnetic moment of 101.2 units. This 

 new magnet (Q") had a moment 129.5 in a field of 9.07 gausses, and 

 a moment 140.2 in a field of 19.93 gausses, when the field was slowly 

 increased. The same mica vane (x) was used as in the work with Q'. 



The results of measurements made upon photographic records 

 made with fields of seven different strengths appear in the next table. 



1.23 1808 0.0222 0.0137 



0.81 4396 0.0283 0.0114 



At another time a long series of observations were made with the 

 same system, under somewhat different initial circumstances of field 

 and perhaps of moisture in the atmosphere, with the results given 

 below. 



TABLE XII. 



