1450 
given by 
Lo=—oaSn2=p hep 
If we take for g a mean value of 6367000 meters and for 
1 
© 507 then expressing A p in seconds: 
Ao=104 Sin2pAgpmm. 
The amplitude Ap of the latitude variation seems to be variable, 
as shown by the investigations of Dr. Zwiers; as mean value I take 
A g¢ —0',16, then for Helder with a latitude of about 53°, 
Ae] 16 mm. 
The displacement of water that is necessary for this change in 
the surface of the sea will be lessened by the attraction of the earth; 
Newcoms in his paper (M.N.R.S. vol 52 p. 336) estimates that the 
displacement is only half as great: Ag would be in this case about 
8 mm. 
The sea level is measured with reference to the solid earth, so 
that, in order to determine the relative variation of the sea level, 
one must also know the variation in shape of the solid earth, 
which of course depends upon its rigidity. In my former publication 
of 1894 I had deduced from a very approximate theory and very rough 
estimates, that the amplitude of the water movement would be about 
4.5 mm. I do not venture to give such a theoretical deduction any 
more, especially as so little is known about the rigidity of the earth; 
whereas SCHWEYDAR found by observations with a horizontal pendulum 
at Potsdam, 
7.6 Pe 10 
for the coefficient of elasticity of the earth, Harp of Karlsruhe 
deduced a much smaller value in exactly the same way from 
observations with horizontal pendulums in Freiberg and Durlach, 
namely 
é 3.2 >< 10" and 3.010 
So long as this great uncertainty about the elasticity of the earth exists, 
estimations are of little value, and we can only state that the theo- 
retical value of the amplitude of the variation of the sea level is of 
the same order as that which is deduced from the observations. 
These various considerations confirm the opinion, that the periodic 
variation of the sea level in 431,24 days, as it is deduced from the 
observations, is real within the limits of the probable errors and that 
it is a consequence of the latitude variation. 
I think it is of importance to apply similar calculations to other 
long series of sea levels, as they might contribute towards the 
determination of the coefficient of elasticity of the earth. 
