( 1233 ) 
As has been noticed in the previous communication the method 
followed of measuring off the distances mentioned above gives twice 
the amplitude multiplied by 1— cos da (@=angular velocity per 
hour) for the semi-diurnal tides as the argument varies in 3 hours 
not 90°, but 3a. 
For the diurnal tides twice the amplitude multiplied by 1 — cos 6« 
is obtained. 
The deflections have been measured off corresponding to the time 
signal, given 5,5 minutes before Batavia time; the arguments have- 
been corrected accordingly. 
The values of the tides mentioned above as found by means of 
the records, and also their theoretical values on the assumption of 
an absolutely rigid earth, are: 
July 1, 1909, noon. 
M,, E—W observed value 0".01120 cos (2t—58°.0) *) 
theoretical _,, 0".01544 cos (2t—45°.5) 
M,, N—S observed value (0.00848 cos (2t—356°.9) 
theoretical _,, O".00167 cos (2t—315°.5) 
K,, E—W observed value 0".00277 cos (2t—245°.8) 
theoretical ,, ~~ 0".00229 cos (2t—269°.8) 
O, N—S observed value O".00644 cos (t—38°.2) 
theoretical _,, 0".00700 cos (t—312°.8) 
K,, N—S observed value O".00449 cos (t—313°.6) 
theoretical _,, 0",00945 cos (t—359°.8) 
P, N—S observed value 0".00645 cos (t— 84°.2) 
theoretical _ ,, 0".00291 cos (t—9°.2) 
North and West are reckoned positive; July 1, 1909, noon has 
been taken as the beginning of time-reckoning. 
Although the E—W components, but for a somewhat excessive 
value of the K, amplitude, closely agree with the theoretical values, 
the N—S components on the contrary show considerable deviations. 
That this disagreement is not due to errors of the instrument is 
proved by the following values for the N —S component of the M, 
tide, calculated for each hour. 
1) Owing to an error in the calculation, the difference between the observed 
and the theoretical values of the argument is not the same as that given in the 
earlier communication. 
81 
Proceedings Royal Acad. Amsterdam. Vol. XIII. 
