46 Proceedings of the Royal Physical Society. 
regard to the general behaviour of the river between Cairo 
and Thebes. In February and August, as is shown in 
Table VII., the temperature of the Nile at its mouths is 
near that of the surface of the Mediterranean. In May 
the Nile would be about five degrees warmer, and in 
November about five degrees cooler. As far as the 
temperature is concerned, there appears, therefore, to be 
but little bar to the migration of animals between the river 
and the sea. 
TABERM VEL, 
Comparison of the Temperature of the Nile at its Mouths 
wih that of the Surface- Water of the Mediterranean. 
| 
| Locality. | February. | May. August November. 
: eer 
Mouths of the Nile, : 62 i2 79 66 
Mediterranean, : ; 62 67 78 71 
Nile difference, . ° | 0 his ASB8) apt 5 
10. The Nile possesses a thermal regime peculiarly its own, 
and strikingly different from those of other great rivers, such as 
the Amazon, the Congo, and the Mississippi. A comparison 
of the Nile with other great rivers of the globe will not only 
give prominence to the distinctive features of its thermal 
regime, but will also indicate the road we must follow to 
arrive at some explanation. But it will be at first necessary 
to consider how small rivers differ from large rivers in these 
matters. It has been abundantly proved, and especially by 
Forster in his “Memoir on the Rivers of Central Europe,” 
that rivers of ordinary size in these latitudes, when freed 
from the controlling influences of their sources in mountain 
1 It is, however, probable that the Yangtse and the Brahmaputra, when 
more fully investigated, will be found to resemble the Nile in some points. 
According to the data supplied by Captain Blakiston, the Upper Yangtse is 
nearly four degrees cooler than the air; and I have shown in the first part of 
this paper that the Bralmaputra issues from the Himalayas at a temperature 
which is in September quite thirteen degrees cooler than the air. 
