J24 



in taking into account in the calculation of the free path of the 

 electrons all the frequencies which play a part in the specific heat 

 has succeeded in explaining this peculiarity : the resistance according 

 to his theory diminishes at very low temperatures only as T^ or 

 as T^!z, (depending on the choice of a subsidiary hypothesis). But 

 then it becomes much more difficult to explain the extremel}^ small 

 value of the possible micro-residual resistance by considering the 

 super-conducting metal simply as a metal with slightly modified 

 properties. It thus seems as if at the vanishing point something 

 occurs by w4iich the small frequencies lose their influence on the 

 resistance although they continue to play a part for the specific heat. 

 The spectrum of the frequencies of the vibrators which are operative 

 in the resistance would thus become limited to a few high frequen- 

 cies or at least be cut off on the side of the small frequencies, in 

 the same way as this happens according to Debije on the side of 

 the high frequencies '). 



Astronomy. — "Investigation of the inequalities of approximately 

 iiiontldy period in the longitude of the moon, according to the 

 meridian observations at Greemoich." By J. E. de Vos van Steen- 

 wijk. (Communicated by Prof. E. F. vais de Sande Bakhuyzen). 



(Communicated in the meeting of April 25, 1913). 



It is now about a year ago that Prof, van de Sande Bakhuyzen 

 brought under my notice the calculations that he and others had 

 made to determine the corrections needed by Hansen-Newcomb's tables 

 of the moon, which still show systematic deviations. I willingly 

 undertook to continue his calculations on the errors of the longitude, 

 and gratefull}- acknowledge his frequent advice and readj- helpfulness. 



My investigation is confined to the inequalities in the longitude of 



transversal kind. Perhaps above the vanishing point only two vibrations play a 

 part in the resistance, a transversal and a longitudinal one, so that according to 

 Planck the small frequency becomes prominent at the lower temperatures, and at 

 the vanishing point this frequency changes into a very high one, so that the ori- 

 ginal higher one assumes the more important part. 



A rotation in opposite senses of two neighbouring atoms with small frequency 

 above the vanishing point, might perhaps, by the atomic surfaces overlapping 

 below the vanishing point, change into a rotation with high frequency. [The 

 caloric investigation of what happens in passing the vanishing point will throw 

 light on this question. As to the specific heat above and below the vanishing 

 point compare the addition to note 1 page 117. 



^) This raises the question whether above the vanishing point also the small 

 frequencies do not in some way lose their influence on the resistance all the more 

 the smaller they are. 



