310 Proceedings of the Royal Physical Society. 
Humphreys and Lieutenant Abbot, and those for the Yangtse 
by Captain Blakiston, some valuable data on the effects on 
large rivers of running with the latitude or the longitude 
are disclosed. The subjoined comparison will afford an 
example. 
Air Water 
Mean. Mean. Difference. 
Mississippi at New Orleans, in March 1851, | 68°°2(F.) | 50°°7 | Water —17°°5 
+ 5 », 1852, | 64°°8 ,, | 50°-7 | Water—14°°1 
Lower Nile, in March 1885, . : . | 66°°3.,, | 68°°3 | Water-+-2°:0 
The localities of observation come near to each other both 
in latitude and in their relation to the same isothermal line, 
and as might have been expected, the air means are not far 
apart; but the water means are wide asunder, and whilst the 
Mississippi, running from the temperate regions towards the 
equator, is from fourteen to seventeen degrees cooler than the 
air, the Nile, after coursing away from the equator, is two 
degrees warmer than the air. 
To collect the observations already published, and to 
encourage observers in this country and in other parts of the 
world to devote their attention to this interesting inquiry, 
would, I venture to think, be objects worthy of the efforts of 
a learned society; and one might humbly suggest to scientific 
societies in distant places the advantage that might accrue to 
science from properly directed investigations of this kind. 
For instance, in the case of the Yangtse, observations at the 
same time at Ichang, Hankow, Kiukiang, and Chinkiang 
might with no great difficulty be instituted; at Hankow the 
temperature of the main river might be compared with that 
of its tributary the Han, and, as indicated by Blakiston’s 
observations, the changes of temperature produced on the 
Yangtse by the inflow from the Tungting and the Poyang 
Lakes would prove well worthy of study. Blakiston remarks 
' that Lieutenant Poole, of H.M.S. “ Havoc,” whilst stationed at 
Kiukiang in 1861, made regular observations of the tempera- 
ture of the river. Abundant materials must occur in the 
