( 241 ) 



condensation, il is desirable that the eapillaiy at the jilace wliere the 

 temperature is between T and 7'" shoiiUI not be (oo narrow. Moreover 

 the capiliary is snrronnded by an air jacket />^, made of' a glass tube 

 tightly closed with india-rubber rings />„ and iish-glue. To avoid 

 diflfusion the other portion of Ihe eapillarv <i'\ nnisl be narrow. 



If by [)revious detei-minalions with the dew-poijil ap|>ai'atns we 

 have determined ./;,.,//' (as a tirst approximation it will in some eases 

 be possible to use a jireliminary if'-snrfaee as eonstiueted in Supple- 

 ment N". 8 see p. 222), it is easy to a|)i)ly the eoi-rection necessary to 

 derive the composition of the investigated licpiidphase at 7' from x , 

 the original composition. On the piezometer divisions the volume of 

 the vapour is read. Let ]\, be this volume reduced to normal cir- 

 cumstances and corrected for the tirst vii'ial coefficient /> (comp. for 

 instance the continuation of this paper), let 1^ be the entire volume 

 of vapour and liquid, measured and corrected in the same wa\', 

 the]i Vi^=V — W is the volume of gas, measured and corrected in 

 the same way, which would form the liquid [thase. 



Hence : 



^^''^^^ ^ — V- V, — ~ ^ + "f ^ ' ~ "^'^'^ "^ • " 



If we operate under moderate pressures, the correction will be 

 always small and even if ■/'„/>7' is not xery accurately known, it can 

 be a[)plied in a satisfactory way. 



Astronomy. — "A uftn lucthod of mterj)olrft/'ou irifh coinptmsation 

 applied to till' I'cdvctlon of the vorvect'iou.^ and die rates of the 

 standard cloel- of die i)t)xerraioni at Leijden, Ilonwr 17, 

 detei'inlned hij die ol)seri'iit'toiis iritli the transit circle in 1903." 

 By J. Wekdkr. Conununicated by Dr. H. (1. van uk Sande 

 Bakhuyzen. 



§ 4. In the Proceedings of Now 29, '1902 occui-s a paper "On 

 interpolation based on a suppc^sed condition of miniiuum," of which 

 the ])resent pai)er is to be considered as a continuation; this explains 

 the numbering of the sections. In order to interjK)late between the 

 ordinates -S' belonging to the abscissae if = ^/, !> . . . ij, :, 1 ha\e there 

 determined the interpolating cui'\e foi- wliicli the total sinuosity 



-/(fj 



(d has the least \alue. 1 found that between two sue- 



