163 
of Edinburgh, Session 1884-85. 
and November, by means of the registering thermometer, was 8° *7, 
and the average 1 0, 9. It is almost certain, arguing from analogy, 
that the daily range is, like the annual range, greatest in the river 
and least in the sea. 
The number of observations made at depths beneath the surface 
has not been so great ; but a considerable mass of facts has been 
accumulated on the subject of the bathymetrical distribution of 
temperature in the Firth. 
The surface, bottom, and intermediate temperatures were regularly 
ascertained at Inchgarvie in from 30 to 40 fathoms • at Inchkeith in 
from 15 to 20 fathoms ; and near the Isle of May, where the depth 
varied from 20 to 25 fathoms. Table Y. gives the means for each 
month, and for the summer and winter periods. 
From June (or probably May) to September the water at the 
surface is warmer than that below ; but from October to April this 
effect is reversed, the water at the surface being then colder. It 
was pointed out some months ago* that the density of bottom water 
in the Firth was always slightly greater than that of surface water 
at the same temperature, and it is probable that the difference in 
density is sufficient to account for the apparent anomaly of cold 
water overlying warmer water during at least half the year. The 
reductions necessary to settle this point are tedious, and have not 
yet been completely worked out. 
Table VI. 
1. 
2. 
3. 
4. 
Alloa to 
Blackness. 
Blackness to 
Oxcar. 
Oxcar to 
Inchkeith. 
Farther Seaward. 
Surf. 
Bot. 
S.-B. 
Surf. 
Bot. 
S. -B. 
Surf. 
Bot. 
S.-B. 
Surf. 
Bot. 
S.-B. 
Mean for May to ) 
September, . ) 
57 T 
56-4 
07 
537 
51-4 
2-3 
54-2 
52-2 
2-0 j 
52-5 
51-3 
1-2 
Mean for October > 
to January, . j 
45*2 
45*8 
-0-6 
44-9 
45-9 
-1*0 
47-6 
48-4 
-0-8 
50*8 
51-2 
-0-4 
Mean for the Year, 
50-0 
50-0 
o-o 
49-3 
48-6 
0-7 
51-3 
50-6 
0-7 j 
517 
51-2 
0-5 
Table YI. gives the seasonal means for all the comparisons of 
bottom and surface temperatures in the four divisions of the Firth, 
* “On the Salinity of the Water in the Firth of Forth,” Proc. Roy. • Soc . 
Edin., xiii. p. 32. 
