THE SOURCE OF THE NILE. 667 
tity of vapour which is here driven fouthward before the 
Etefian winds. Now, allthat country between Gerri and Syene 
is flat and defert,fo that this interruption is wanting; and it is 
owing tothe fame caufe, that the bounds of the tropical rains 
do ftop farther to the fouthward as you travel weftward, and 
in place of lat 16°, whichis their limits at Gerri, theyare con- 
fined within lat. 14° in that part of the kingdom of Sennaar 
- which lies fouth and weft of. that capital, where all is free 
from mountains till you come to thofe of Kuara and Fa- 
zuclo. 
Yer although the fun’s influence when at its greateft, is 
not ftrong enough to draw the boundaries of the f{ummer’s 
rain farther north than Gerri, all the time that it is in the 
tropic of Cancer at its greateft diftance, thefe rains are then 
at their heavieft throughout all Abyflinia ; and Fgypt,andall 
its labours, would foon be {wept into the Mediterranean did 
not the fun now begin to change its {phere of action ‘by ha- 
ftening its progrefs fouthward. 
. From Syene the fun pafles over the defert, and arrives at 
Gerri; here he reverfes the effects his influence had when 
on his paflage northward ; for whereas, in his whole courfe 
of declination northward, from the Line to Gerri, he brought 
on the rains at every place where he became vertical, fo 
now he cuts off thofe rains the inftant he returns to the 
zenith of each of thofe places pafling over Abyflinia in his 
journey fouthward, till arrived at the Line, in the autumnal 
equinox, his influence ceafes on the fide of Abyffinia, and 
goes to extend itfelf to the fouthern hemifphere. And fo 
precifely is this ftupendous operation calculated, that, on 
the 25th of September, only three days after the equinox,the 
4 Pee Nile 
