892 



tigiire of tlie earth wonlil iiidiL-iitc ii greater value tor (ho ellipticily. 

 Amongst these perturbations tliere are four which have a somewhat 

 considerable coefficient : 



1. a motion of the perigee; 



2. a motion of the nodes; 



3. a periodic inequality in the longitude; 



4. a periodic ineciuality in the latitude. 



The first of these, according to our results, would lead to 1 : 294.3, 

 according to Newcomb's to 1 : 294.6 ; the second, according to Neavcomb's 

 results, would yield 1:294.3 and the 4f'\, according to Newcomb, 

 1 : 293.7, while the 3"^ which has a period of 18 years cannot be 

 used for our purpose on account of the unexplained inequalities of 

 long period in the mean longitude. Are these differences to be 

 regarded as real and woukl therefore the measurements made on 

 the surface of the earth not lead to an accurate determination of 

 the difference in the moments of inertia ? 



On account of the possibility that other circumstances may 

 exercise an influence upon the motions of the perigee and node, the 

 periodic inequality in the latitude, which has a monthly period, 

 would certainly be the most likely to yield a decisive answer to 

 this question, if it were not that an error in the assumed obliquity 

 of the ecliptic has precfsely the same influence upon the declination 

 of the moon as the inequality in the latitude. (See also Newcomb's 

 very interesting Addendum to Chapter XI, p. 226). 



Physics. — "Magnetic researches. XI. Modification in the cri/omagnetic 

 apparatus of Kamerlingh Onnes and Perkier." By Dr. E. 

 OosTERHUis. Communication N°. 139/> from the Physical Labo- 

 ratory at Leiden. (Communicated by Prof. H. Kamerlingh 



Onnes). 



{Communicated in the meeting of January 31, 1914.) 



In the researches on paramagnetism at low temperatures, described 

 in N^^VI, VII, and VIII of this series (Comm. NM29^ 132^ 134'0> 

 an apparatus was used, in the main the same as that constructed 

 by Kamerlingh Onnes and Perriek, of which a complete description 

 is found in Comm. N". 139". 



In one particular, however, a change was made in the apparatus. 

 The apparatus so changed, which was briefly indicated in § 1 of 

 Comm. N°. 129'', is here more fully described. The force acting 



