oe 
hwwer Temperature. 
Il. River Temperature. Part Il. The Temperature of the 
Nile compared with that of other great Rivers. By H. 
B. Guppy, M.B., F.R.S.E. 
(Read 16th January 1895.) 
From the considerable number of disconnected observa- 
tions on the temperature of the Nile, which have been 
already published, it might be inferred that we ought to be 
well acquainted with the thermal behaviour of this famous 
river. Such, however, is not the case; and in fact, as far as 
I am aware, few if any persons have endeavoured to put the 
data into form. In this paper I have attempted this task, 
not without misgiving, as the subject is one of much com- 
plexity. A previous study of other great rivers, at lencth led 
me to hope that, by the free employment of the comparative 
method, I might be able to distinguish the peculiar features 
in the temperature of the great river of Egypt. Fortunately 
in this end I have been much assisted by the large number 
of observations to be found in the Journal of Robert Hay, 
which exists in manuscript in the British Museum.? 
The first reference to the temperature of the Nile that has 
come under my notice is to be found in the “ Pharsalia” 
(x. 275), when Lucan is alluding to the visit of the emissaries 
of Alexander to Egypt. ‘‘Nilum videre calentem,” he 
observes, yet we are in doubt whether to attribute the 
epithet to poetic fancy or to the exigencies of the metre. 
The Nile, however, is not a warm river. In truth, when we 
reflect on its numerous opportunities of acquiring a high 
temperature, this river is remarkable for its coolness. 
Amongst the earliest investigators of its temperature was 
M. Coutelle, a French savant, one of the many distinguished 
men of science who accompanied Napoleon in his Egyptian 
expedition between 1799 and 1801. His observations were 
confined to a few weeks in the summer at Phile; but they are 
only incidentally mentioned in his meteorological tables given 
1 The Fahrenheit scale is used throughout this paper. 
* T intend to deposit in the library of the Royal Physical Society, Edin- 
burgh, a copy of these meteorological observations as far as they are con- 
cerned with the river temperature. 
VOL. XIII. Cc 
