< 463 ) 
The new value of the yearly sinking of the level of the ground is 
not very accurate, as appears from the pretty high value of the 
mean error. To be able to judge about this in another way I have, 
just as in the first series, excluded some very divergent values, viz. 
the yearly means of 1864 and 1877; if we calculate the value of 
b from the 14 remaining yearly means, we find for it 0.00 cm., in 
other words: while from 16 yearly means a sinking of the ground 
of 0,3 cm. would follow, it follows from 14 of the same yearly 
means that the level of the ground has neither fallen nor risen. 
I believe that we are justified in deriving from this investigation 
that neither from the first nor from the second series of the readings 
of the gauges communicated by Mr. Ramaer any conclusion may be 
drawn with reference to a rise or a fall of the level of the ground. 
H. G. VAN DE Sande Bakhuyzen. 
Note on the sinking of the level of the ground in recent 
years. By H. E. de Bruyn. 
To examine whether of late years according to the observations 
on the gauges the level of the ground has risen, or whether it has 
sunk compared with the mean sea-level, the following remarks may 
be given. 
Both in the case that the level of the sea rises, which in my 
opinion is the most probable case, and in the case that the land sinks, 
this will not take place regularly, i. e. every year to the same amount, 
but because nothing is known about this, we can only assume the 
sinking of the land with respect to the sea-level as regular, so represent 
the mean level of the sea with respect to the zeros of the gauges 
as a straight, ascending line. 
Now the mean yearly sea-level at any point differs a constant 
quantity with the height of half-tide. So the rise of the mean sea- 
level can be derived from the height of half-tide. 
The greatest difficulty in these considerations is the possible shifting 
of the zeros on the gauging rods. As these shiftmgs are much less 
frequent for ordinary than for registering gauges I shall only consider 
ordinary gauges. 
The yearly sea-level depends in the first place on the wind. The 
deviation in consequence of the influence of the wind is great com¬ 
pared with the possible differences in the mean sea-level over some 
years in consequence of the sinking of the ground. Now it appears from 
the observations that the influence of the wind is generally in the 
