Or SEA-WATER IN THE DIFFERENT PARTS OF THE OCEAN. 
231 
When afterw ards, in quiet sea, without current, a diver went down to save the passen- 
gers’ goods, he found a violent current from the North. To the same class of pheno- 
mena belongs also the observation that large deep-going vessels not unfrequently go on 
in the Sound against surface-current, where smaller vessels do not succeed. 
This under-current of Elsinore reaches often, and perhaps always, the harbour of 
Copenhagen, which I ascertained by a series of observations for which the laying of 
gas- and water-pipes offered me a good opportunity. To carry these pipes under the 
harbour, from Copenhagen to Christianshaven, on the Island Amager, a tunnel was pro- 
jected through a solid hard limestone of the chalk formation, which lies under Copen- 
hagen, its harbour, and its neighbourhood. When the tunnel was completed, it was 
found that the sea-water slowly filtered through the limestone, and fell down in drops 
from the roof of the tunnel. Comparative analyses would show how the water of the 
bottom of the harbour differed from that of the surface, and I might at the same time 
clear up another rather important question. It is generally known that the question of 
the formation of the dolomites, or the double carbonates of lime and magnesia, has 
excited a great interest, and many theories have been proposed about their formation. 
I myself have shown that a solution of carbonate of lime in carbonic acid water, when 
poured into sea-water, precipitates both carbonate of lime and carbonate of magnesia, but 
that the quantity of magnesia increases with the increased temperature in which the 
decomposition takes place. Neutral carbonate of lime thrown into sea-water would 
however, even at the boiling-point, not precipitate any carbonate of magnesia. It might, 
however, be a question of time, and it might be possible that such a decomposition 
would take place if sea- water during a long time was in close connexion with solid 
carbonate of lime. This would be the case if sea-water slowly filtered through 30 feet of 
solid limestone, which it does in the tunnel. We cannot, of course, expect to obtain 
any result by comparative analyses of the limestone ; any change in the composition of 
this great mass of limestone would be so small that no result could be drawn from it, but 
we might analyze the sea-water filtered through the stone, and determine very small 
changes in its composition. Thus a series of comparative analyses of the sea- water from 
the surface of the harbour, of that from the bottom of it, and of the water filtered through 
the limestone into the tunnel, would show, first, whether the under-current from Elsinore 
reaches the harbour of Copenhagen ; and secondly, whether the limestone roof of the 
tunnel acts upon the salts of magnesia in the sea-water which filters through it. 
The experiments were made in the following way: once a week, from the 3rd of 
March to the 25th of April, 1852, one sample was taken of sea-water from the surface 
of the harbour over the tunnel, another sample from the bottom of the harbour at the 
same place, and a third sample was collected from the filtering water in the tunnel. 
The mean of these analyses gave, 
For the surface 15-845 per 1000 salt 
For the bottom of the harbour . 17-546 „ 
For the tunnel 18-315 „ 
