42 Proceedings of the Royal Physical Society. 
conditions in this region would naturally vary a_ little. 
Chaix, Schnepp, and Russegger, for instance, found the air 
in January to be warmer between Assouan and Thebes than 
between Thebes and Cairo. Villiers Stuart, on the other 
hand, found the air cooler above Thebes than below it. 
The observations of Mr Villiers Stuart are not only 
valuable from the indications they afford, but also as an 
example of how much may be done with little trouble. It 
will be noticed in the analysis I have made of his observa- 
tions in Table V., that during the first part of his ascent the 
air and water temperatures did not vary much; whilst farther 
up the river they both dropped considerably, the water 
temperature falling the most. On- looking at his daily 
register, it appears that between Cairo and Esneh the river 
temperature at sunrise was always 66°, and that between 
Esneh and Korosko it fell steadily to 58°, and there remained, 
during the remainder of his ascent for the next four days, 
until Abu Simbel was reached. This was accompanied by a 
fall of the air temperature much less in extent,namely, from 65° 
to 60°, the two temperatures having crossed in the interval. 
The altered relation of the air and water temperatures in 
winter will be also clearly indicated by the comparison of the 
sunrise observations given in Table XV. Unfortunately, the 
isothermal chart of Buchan for January does not lend itself 
to our aid here, there being some discrepancy between the 
data employed and the course given to the isotherm of 60° 
in the vicinity of Cairo, The mean temperature for January 
at Cairo between 1868 and 1881 was 54°:2, and I will take 
this as my datum for the next conclusion, 
TABLE III. 
Table of General Results for January in the Nile. 
| Locality. appecimate,|. Air. | (Water, | Woe 
| 
| — = 
Between the First and Second | ERG ie ee : r 
Cataracts, . ‘ isi oo ae cgi ae 
Between Assouan and Minieh, | 24°-28° 58°7 60°6 +1°9 
WiCuiro eM tee “Po ea ese 542 | 60-0 | +5°8 
Note,—The Cairo results are only approximate, 
