of Edinburgh, Session 1884-85. 
157 
where the tangent is horizontal would be a critical temperature of a 
peculiar nature, both forms of the above law applying to it. I hope 
to he able to settle this point in the experiments above proposed. 
3. Not3 on the Thermal Effects of Tension in Water. By 
G. K Stewart, Esq. Communicated by Prof. Tait. 
4. On the Temperature of the Water in the Eirth of Forth. 
By Hugh Robert Mill, B.Sc., E.C.S. (Plates VI., VII.). 
The temperature of water can he ascertained much more easily 
than that of air, and with far greater accuracy ; yet comparatively 
little has been done by meteorologists in the way of obtaining data 
hearing on the distribution of temperature in rivers and in estuaries. 
Some observations of great value have been discussed by Mr Buchan 
in the Scottish Meteorological Society’s Journal,* but these were 
discontinued after a few years. 
It would he extremely interesting, and would lead to valuable 
results, if at a number of stations on the River and Firth of Forth, 
for example, the temperature of the water could be ascertained daily, 
and also the temperature of the tributary streams at short intervals of 
time. The value of such work would of course he enormously increased 
if it could he applied to other river-systems, so as to admit of com- 
parisons between them. A very complete system of observation is 
at present being arranged by the Tweed Commissioners, from which 
interesting results regarding the Tweed may be expected. 
The temperature of a large river depends, in the first place, on the 
temperature of the deep lakes which supply it, where, as on the 
Forth, such lakes exist ; secondly, on the temperature of the feeders, 
which is affected by the temperature of the rain falling, and by that 
of the land over which it runs. In the third place, the colour and 
transparency of the water, depth of river, rapidity of flow, and 
nature of the banks modify the effect of radiation ; and, lastly, 
the proximity of the sea, and consequent effect of tide, must be 
considered. 
Observations have been made at the Scottish Marine Station 
since May 1884, and although nothing final can be said, it has been 
* Jour. Scot. Met. Soc., new series, i. p. 256 ; v. p. 251. 
