1448 
In this series there is again little trace of a periodicity in a period 
of 438 days. | 
Finally I arranged the mean sea levels according to the phases of 
a period of 440.872 days, which is 16-times the period of the monthly 
moon tide Mm. the length of which is 27.5545 days. It is plain that the 
influence of this tide will only be felt to a very small degree in the 
bi-monthly means, as these are the means of two complete periods 
or 55.11 days and 5.7 days. The periodic variation in the bi-monthly 
means will be about '/,, of that which is due to the actual tide Mm. 
After arranging and combining the bi-monthly means I got for the 
sea level at 14 different epochs with intervals of one month 
==") 2.6) mm: 
err 
7,3 
3,4 
pt+++++4 | 
The periodic character is here undeniable, and if we determine the 
amplitude of the Mm.-tide itself from these figures, we get for the 
amplitude 118.0 mm., whereas from the observations in 1892 I 
formerly got for the amplitude 83.4 mm. (Versl. Kon. Akad. v. Wet. 
Vol IL, p. 197). The correspondence is satisfactory, if we consider 
that the error in the observations made in the above series appears 
in the amplitude multiplied by about 16 
These different considerations give me reason to take the value 
found above for the periodic change of the mean water levels in the 
time of 431.24 days as correct within the limits of the probable 
errors. 
The probable error of the amplitude 4.42 is + 1.93, the probability 
that the amplitude lies between O and 8.84 mm. may therefore be 
put at 7. 
7. We have next to discuss the question what the connection is 
