1887.] Dr H. R. Mill on Salinity and Temperature of Firths. 255 
Cromarty, and Dornoch — are practically only those obtained in 
1886, and the time over which their collection extended was much 
too short to make them of more than comparative value. Import- 
ant series of hourly observations, extending over the greater part of 
a tide, were made in each firth, and to these more particular atten 
tion may he paid, as they confirm and extend the results obtained 
on the Spey in 1885, and on the estuary of the Forth at Kincardine 
in May 1886.* 
Inverness Firth . — This inlet is narrow and full of sand-hanks, 
which divide it up into tortuous channels of very slight depth. 
Near Fort George the water is a little over 10 fathoms deep, hut 
further up 5 fathoms is about the average ; and the Beauly Basin 
in which the firth terminates is much shallower. During the days 
on which observations were made, the temperature of water in the 
Inverness Firth was about 56° on the surface. The bottom tem- 
perature was nearly the same in the shallower part of the firth, but 
it fell in a very marked manner towards the sea, being 52°*7 at the 
bottom off Fort George, and 51°*5 off Nairn. The average density 
of the water at stations about 5 miles apart was as follows, but 
the individual readings varied greatly with the tidal phase : — 
Table III. 
Place. Kessock. 
Surface density at 1 5° *56 C., 1*01870 
Bottom ,, ,, 1*01950 
Number of cases, . . 16 
Avocli. 
1*02161 
1*02281 
6 
Fort George. Off Nairn. 
1*02269 1*02465 
1*02397 1*02547 
4 2 
This shows a progressive increase of salinity seawards, and a 
distinctly greater salinity for bottom water at all points. The 
diagram, PI. VIII. fig. 5, represents graphically the distribution of 
wmter density and temperature at surface and bottom, from Kessock, 
past Fort George, out into the Moray Firth, to a position off Covesea 
Skerries. Compared with the Firth of Forth, the rate of increase 
of salinity is very rapid, and the difference between surface and 
bottom more marked in the seaward reaches of the firth. 
Numerous observations were made in the anchorage at Kessock 
Roads, at various depths. The data for surface and bottom only 
need be given here, but these are of considerable importance. The 
* Proc. Roy. Soc. Edin., 1886, xiii. pp. 790-799. 
VOL. XIV. 3/11/87 
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