Remarks. 
1. The height of the piston appears to have an appreciable influence 
on the pressure. This influence was not observed at Leiden in expe- 
riments made expressly for the purpose. 
2. The rotatory velocity has an appreciable influence on the 
pressure. 
3. The direction of rotation has a great influence on the pressure 
with the Utrecht pressure balance. The difference amounts to about 
60 grams for a charge of 60 kg. When the charge is very slight, 
the Utrecht balance can only be rotated in one direction. Hence 
only the charge for righthand rotation is always taken into account 
on comparison with the small Amsterdam balance. On comparison 
with the large balance on Oct. 19 and 20 the Utrecht balance was 
either rotated to the left or to the right, because then the pheno- 
menon had not yet been observed. Afterwards always the mean 
has been taken of the charge for lefthanded and righthanded rotation. 
Result. The vatio of the effective areas appears to be pretty well 
constant, taking into consideration the inaccuracy which is the con- 
sequence of the phenomena mentioned in the above remarks. On 
comparison of the Utrecht pressure balance with the small Amsterdam 
balance, however, the ratio values seem to present a slight syste- 
matic course. 
{t is the intention to continue the investigation of the pressure 
balance in the Amsterdam laboratory, first of all in this direction 
that the value of the effective area will be determined for very 
different values of the charge. The apparatus required for this will, 
however, most likely not be obtainable during the war. 
In conclusion I must express my indebtedness to Prof. KonNsTAMM, 
under whose superintendence I have been allowed to carry out this 
investigation. 
Deventer, September 1916. 
