1184 
We gladly thank all who have assisted us in carrying out the 
measurements, in tbe first place Mr. F. M. Pennine, who was 
entirely responsible for the regulation and measurement of the 
temperatures and the calibration of the resistance thermometers, 
and made all the calculations involved every time; further Miss 
H. van per Horst, who assisted in the temperature measurements 
and carried out and calculated the greater part of the observations 
with the helium thermometer; finally to Mr. G. J. Fri, chief 
mechanic of the cryogenic laboratory and to Messrs. L. and A. 
OUWERKERK, with whom the far from simple management of the 
vapour cryostat was in very able hands. 
