260 Proceedings of Royal Society of Edinburgh. [june 6, 
Table YII. — Observations in Ardjachie Roads , Dornoch Firth. 
Date. 
Hour. 
Wind. 
Tide. 
Depth. 
Temperature. 
Density. 
Air. 
Surface. 
Bottom. 
Surface. 
Bottom. 
Aug. 17 
15 h 0 
N.W., 4 
2h. ebb. 
fm. 
5S 
56-5 
56°8 
55 ‘9 
1-02271 
1-02339 
55 
16.0 
N.W., 3 
3 „ 
5 
... 
56-9 
56-0 
1-02116 
1-02152 
55 
17.0 
N.W., 2 
4 „ 
5 
... 
56-8 
56-9 
1-02100 
1-02137 
55 
18.0 
N.W., 2 
5 „ 
5 
57-0 
56*8 
1-02039 
1-02070 
55 
19.0 
0 
6 „ 
H 
57-2 
56-9 
1-01867 
1-02025 
55 
20.0 
0 
i h. fid. 
3f 
... 
56-9 
57-0 
1-01817 
1-01965 
55 
21.0 
0 
11 » 
4 
54-7 
57 T 
57-2 
1-01815 
1-02011 
55 
22.0 
0 
2i „ 
H 
56-6 
56-7 
1-02054 
1-02118 
55 
23.0 
0 
H „ 
5 
53-0 
56-4 
56-3 
1-02118 
1-02184 
Aug. 18 
0.0 
0 
4| „ 
H 
53-0 
56-4 
56-3 
1-02207 
1-02227 
55 
1.0 
0 
P)1 
55 
5S 
52-5 
56-3 
55-7 
1-02207 
1-02408 
55 
2.0 
0 
H. W. 
6 
50*3 
56-2 
55-3 
1-02189 
1-02472 
as regards vertical distribution of salinity. The following reading 
showed a new condition altogether’; the bottom had increased in 
salinity very greatly, and continued to do so until high water ; the 
surface, on the other hand, remained constant, and even showed a 
slight decrease. This means that after the water had been 
thoroughly mixed, sea- water of greater density began to push its 
way along the bottom, and the surface current of brackish water 
being no longer driven up stream by a wall of uniform salinity, 
resumed its downward course very slowly, and passed over the 
salter water without mixing with it : in fact, ebb had begun on 
the surface, while flood-tide continued down below. It thus 
appears that, so far as the tidal movement of water is concerned, 
the bottom of the channel in an estuary is before the surface in 
phase. 
The question of tidal currents in estuaries is a very important 
one ; but for its thorough investigation it requires the simultaneous 
■work of several assistants, and a large enough staff to carry on 
uninterrupted observations for several successive tides. This I 
