1887.] Dr H. R. Mill on Salinity and Temperature of Firths. 253 
given date than it was at the same date in some other year is of 
trifling importance. What must be compared, with regard to varia- 
tions of temperature at one place, is not the absolute degree of 
warmth at a particular depth, but the vertical distribution of warmth 
and the annual changes of this in form and amount. 
The following statement of the conditions of a section, from the 
Ord of Caithness to Burghead on August 19th, will illustrate the 
distribution of salinity in the open firth at that date. Station I. 
was about 1 J miles south-east of the needle of Ord, the others each 
10 miles farther south, the last being close to Burghead. 
Table I. 
Station. 
I. 
II. 
III. 
IY. 
Density of surface water at 15°‘56 C., 1 ’02588 
1-02581 
1-02585 
1-02510 
,, bottom ,, 
,, 1-02585 
1-02587 
1-02585 
1-02573 
Depth in fathoms, 
19 
26 
26 
10 
State of tide, 
. . 4| hrs. fid. 
\ hr. eh. 
2f hrs. eb. 
4 hrs. eb. 
This shows a very slight freshening towards the southern shore. 
The increase of salinity seaward was shown, by many isolated ob- 
servations, to be gradual but steady, although no regular east-and- 
west section was made. The temperature from north to south, on 
August 19, was as follows, the figures given being corrected to read- 
ings of the Kew standard : — 
Table II. 
I. 
II. 
III. 
IY. 
Hour, 
• e 
13. 45 
15.10 
17.15 
18.30 
Air temp., . 
. 
55-2 
57-0 
55-5 
58-0 
Temp, of sea, 
0 fthm., 
55-0 
55-3 
54-3 
56-3 
9 9 
1 „ 
— 
55-2 
— 
56-2 
9 9 
2 „ 
54-7 
— 
54-2 
56-2 
9 9 
3 „ 
54-3 
54-2 
— 
— 
99 
5 ? 5 
53-5 
53-8 
53-5 
54-7 
9 9 
6 „ 
— 
53-8 
— - 
— 
9 9 
7 „ 
51-9 
53-2 
— 
— 
9 9 
8 „ 
— 
53-1 
— 
— 
9 9 
9 „ 
— 
51-4 
— 
53-2 
9 9 
10 „ 
— 
— 
52-3 
9 9 
12 „ 
— 
51-2 
— 
9 9 
15 „ 
— 
51 T 
— 
9 9 
18 „ 
51*2 
— 
— 
9 9 
25 „ 
. . . 
51-0 
50-5 
