MISCELLANEOUS NOTES. 
ces seem, at the first glance, sufficiently to explain 
this identity. 
But I do not believe that in this case the difference 
of the latitude has been observed. The mean parallel 
of Egypt is about 27°i.; that of Senegambia 13; differ- 
ence 14°|. If the height of the temperature is impor- 
tant, as it undoubtedly is, amongst the causes which 
encourage to a certain extent some species of vegeta- 
bles and animals, it must be concluded that Egypt 
is the vrarmest region of northern Africa in propor- 
tion to its latitude. The mean temperature of Egypt 
is, actually higher than that of the Senegal : this 
Avas far from being suspected prior to the obser- 
vations of the Egyptian Institute; and Baron Hum- 
boldt did not introduce his Memoir on the isothermal 
lines till after having long retained doubts, which the 
tables of Messrs. Nouet and Coutelle dispelled. 
Thus, the isothermal line of Egypt would make a 
large angle with the equator. Mount Atlas is too far 
distant to explain the fact ; the mountains of Sene- 
gambia are not sufficiently elevated ; we are, there- 
fore, led to seek the cause in the vicinity of the Sahara, 
the vast radiation of which must incessantly attract 
the lower strata of a warmer atmosphere, such as that 
of Senegal and of the more remote districts, on 
account of their nearly juxta-equatorial position : so 
that the mean temperature of Senegambia would, but 
for this cause, be much higher than it is, and far 
higher than that of Egypt. 
