River Temperature. 
51 
characteristic only of its higher courses, and gradually 
lessens as we descend the river, until it disappears at Cairo. 
The coolness of the Mississippi is most developed near its 
mouths, as at New Orleans, and disappears as we ascend the 
river and arrive at Memphis. 
(f) The Nile during any part of its course below the Second 
Cataract does not acquire the summer temperature of the Mis- 
sissip pt. 
ABLE OX. 
This contrast is well brought out in Table X. 
Comparison of the Annual Mean Temperatures and of the 
Ranges of the Monthly Mean Temperatures of the Nile 
and the Mississippi. 
Year's Mean. 
Range of Monthly Means. 
phis in 1850, 
| Nile at Cairo, ; 
| Nilebetween Minieh 
and Assonan, 
| Nile between nist | 
Locality. Lat. N. | Air. Water. 
| Air. | Water. W. diff. 
| Min. | Max. |Range.| Min. | Max. 
| a (nit 
Mississippi at New ane » 2. a7 | ar. Bl P 
isc, \ 30° | 67-6 | 63-9 | —3-7 | 45°8 | 82°8 | 37-0 | 40-8 | 83-4 
Mississippi at New | ° ; : “5 | 59-9 | Q1- , QF ; 
Orleans in 1852, J 30 69°8 | 64°3 | —5°5 | 52:2 | 81°8 | 29°6 | 42°5 | 85°0 
Mississippi at New ° 2 a ; ‘ ‘ ao lta 9 
Orleans, mean, \ 30 68°7 | 64:1 | —4°6 | 49°0 | 82°3 | 33°3 | 41°6 | 84°2 
Be sippi at ‘ibaa 36° 9’ |60-4| 60-9 | +0°5| 42-1 81-1/ 39-0 39°3| 84-7 
30° 3’ | 71:2) 71°0 | —0°2| 54:2 | 85:0 | 30°8 60°0 | 79°5 
28°6’-24°6'| 74:5 | 71°6 | —2°9 | 58°7 | 86°3 | 27°6 | 60°6 | 79°7 
| 
and Second Cata- || 24°-22° | 80:2) 72:9 | —7°3| 64:3 | 92°1| 27-8 | 61°6 | 82°6 
mACESS Bee Et dS ) | | 
Vote. —Captain Humphreys and Lieutenant Abbot are my authorities for 
the Mississippi at New Orleans, and Lieutenant Marr for the same river at 
Memphis. 
The highest mouthly mean for the river at New Orleans in 1846 
was, according to Professor Riddell, 83°°7 ; whilst Dr Drake places the lowest 
in 1843, off the same city, at 41°. 
Dr Dowler placed the extreme range of 
the temperature of the river at New Orleans, in the course of the year, at 
from scarcely 40° to nearly 86°. 
(g) Whilst, as before shown, the difference in temperature 
between the Nile and the surface of the Mediterranean can 
never be great, it is far otherwise in the case of the Mississippr 
and the Gulf of Mexico. 
Observations made by Dr Drake in 
