602 
Proceedings of the Royal Society of Edinburgh. [Sess. 
XXXVI. — Dr O. Pettersson’s Observations on Deep Water Oscilla- 
tions. By E. M. Wedderburn, W.S. (With a Plate.) 
(MS. received July 5, 1909. Read July 5, 1909.) 
Dr Pettersson has recently published a paper on “ Gezeitenaehnliche 
Bewegungen des Tiefenwassers ” ( Publications de Gir Constance , No. 47), in 
which he describes certain movements in the deep waters of the Skagerak 
observed in January, February, and March 1909 at the Swedish station Borno, 
in the Gullmarfjord, lat. 58° 24' N., long. 11° 33' E. The observations were 
taken daily at 12.30 p.m. by means of soundings made through the ice. 
The diagram accompanying this paper is a reproduction of a diagram 
prepared by Dr Pettersson, and shows the observed variations in the 
position of the isotherms and isohalines. No observations appear to have 
been made on 7th, 8th, 10th, and 11th February, nor from 15th to 18th March, 
so that there are large interpolations on the diagram. Fig. 1 is a map of 
the Skagerak, the point of observation being marked by a cross. 
There is a marked discontinuity in the density of the water of the 
Skagerak at this time of year at a depth which averages about 20 metres. 
The presence of this discontinuity is shown in all the observations. The 
following set of observations for 10th March is an example : — 
Depth, 
Metres. 
Temp. 
Celsius. 
Density. 
0 
•05 
1-00212 
10 
'42 
1-02315 
20 
•85 
1-02387 
25 
3-98 
1-02675 
30 
5-41 
1-02670 
40 
5-88 
1 02701 
49-5 
5-95 
1-02701 
The observations show an oscillation in the level of the discontinuity 
with a period of about fourteen days, which Dr Pettersson seeks to explain 
as a long-period tide in the lower dense layer, and states that the moon 
seems to have a tendency to accumulate the deep water of the Skagerak 
against the eastern coast whenever it attains a high northerly or southerly 
declination, and suggests that a yearly oscillation may, in the same way, be 
produced by the influence of the sun. He justly adds, however, “ It is 
difficult to imagine how this attraction can act in a different manner upon 
