254 Proceedings of Royal Society of Edinburgh. [june 6, 
An observation made off Dunbeath Castle (further north than -the 
Orel), in 10 fathoms, gave temperature of 52° ’5 at the surface, and 
52 o, 0 at bottom. Excepting this sounding, the observations of 
temperature showed a warm layer falling from 55° or more at the 
surface to 52° at 6 fathoms on the Caithness coast, and at 12 fathoms 
on the Morayshire side. The minimum bottom temperature was 
50° '5 just on the verge of the deep trough off Burghead. Plate 
VIII., fig. 4, shows graphically the distribution in this section of sur- 
face and bottom density, and of temperature at surface, 5 fathoms, 10 
fathoms, and bottom. In the depression off Troup Head, at a depth 
of 50 fathoms, an observation on August 23rd gave a temperature 
of 54°'8 on the surface and 50° '4 on the bottom. The lowest tem- 
perature of the trip was found on August 10, at the bottom of the 
depression off Covesea Skerries, in 33 fathoms, the thermometer 
reading being 49°’5. A section made from Fort George to this point 
(30 miles) showed a perfectly horizontal and parallel arrangement of 
the isotherms of 50°*5, 51°, 51° ‘5, 52° and 52°‘5, contrasting with the 
dip to southward in the north-and-south section. 
During the month of August the sea temperature on the west 
coast of Scotland was 52° *5, from surface to bottom, off the Mull of 
Cantyre, and in the Arran Basin, 53° or 54° on the surface, falling 
to 47° *5 or 48° at 30 fathoms. The Moray Firth thus appears to 
have been warmer than the western waters during this period. 
The observations made in 1883, although not very numerous, 
are sufficient to show that the bottom water was practically of the 
same salinity then as in 1886; while the surface water near the 
entrance of the Inverness Firth was much fresher at the earlier 
date. This is quite as might be expected, since the summer of 
1886 was exceptionally dry in the north-east of Scotland, and the 
rivers and streams were unusually low. 
Taking into consideration the facts that have been ascertained, 
we conclude that the water of the Moray Firth is the saltest which 
can be found near land in the North Sea, except on the bottom of 
the Norwegian Gully, and possibly in the neighbourhood of the 
Strait of Dover, where no observations have been made. The 
influence of estuaries and rivers entering the Moray Firth appears 
to effect a local and very superficial freshening. 
The data available for the three tributary firths — of Inverness, 
