( 1236 ) 
(relative to Batavia time) is about 200°, whilst its average value in 
Sundastrait (Telok Betong, Java’s 4th Point, Labuan) is 210°. 
It is therefore reasonable to assume that over the whole region, 
where the disturbance exercised on the 4-W pendulum originates, 
the kappanumber varies but slightly from 200°, say not more than 10°. 
If we now calculate the disturbing force and the undisturbed 
earth-tide on the assumption that the kappanumber is 200° and that 
the argument of the undisturbed tidal motion of the ground is 
equal to its theoretical value, then we find *): 
Amplitude disturbing force 0’’.0026 
5, corrected earth-tide OV Mids 
For the proportion between observed and theoretical amplitudes 
in the case of a rigid earth this gives the value 0.76. 
Hecker also found for the 4-W component the factor 0.76, and 
Orzorr*) at Jurjew gives 0.63 as deduced by means of a ZOLLNER 
seismograph. 
If we summarize the results given above, it is in the first place 
evident that great care must be taken in the choice of stations to 
be used for the determination of earth-tides, and that places situated 
in the vicinity of a sea with considerable tides are unsuitable for 
this purpose. 
Further the unsatisfactory results obtained for the K, and P 
tides justify the conclusion that, in order to determine the constants 
of these tides, the instruments should be erected in a place sufficiently 
deep to eliminate tidal motions of meteorological origin. 
It appears, further, that Wircurrt’s pendulum is a very reliable 
and sensitive instrument, well suited for the determination of tidal 
motions and that, by means of its records, the diurnal as well as 
the semidiurnal tides may be determined without changing the 
erection usual for seismographie purposes. 
If only the constants of the apparatus have been determined with 
sufficient care the material at present available from seismographs 
placed in favourable situations might at once be used for tidal 
researches without extra expense and the knowledge of the tidal problem 
might in this way be considerably extended. 
For Batavia it proves to be possible to deduce the semidiurnal 
lunar tidal motion of the ground in the /- W direction notwithstanding 
the disturbance due to watertides. 
Weltevreden, February 12, 1911. 
ay For kappa = 190° and 210° the amplitudes of the disturbing force are respect- 
ively 0”.0025 and 0".0028, of the corrected tide 0".0114 and 0".0123. 
2) Astronom. Nachr. No. 4446. Bd. 186. 
