Situation of Zones without Rain, and of Deserts. 95 
extreme colds nor great falls of snow: the fertile and well 
watered soil produces wheat, lint, sweet melons, water me- 
lons, and grapes ; but to the south, nothing is to be seen but 
gobi, or plains of sand, on which asses and wild horses are 
found in herds of tens and hundreds.” 
This great concavity, however, may in fact be compared 
less to an absolute desert than to a steppe, differing, in re- 
spect of its southern position, from the Russian and Siberian 
steppes : storms occur on its borders in June and July, and 
snow falls in winter ; sometimes even the vegetation of the 
middle sandy portion, after being destroyed by the prolonged 
suspension of rains, is developed with vigour when they again 
abound ; so that in all this we can only see the tendency 
which the savannahs of all parts of the world have to pass 
into the state of deserts. 
Opposite Asia we find only one great island, New Holland, 
placed in the same parallels as Arabia and Hindostan ; but 
its interior being as yet unknown, the absence of rivers, and 
the dryness of the winds over the whole extent of its coasts, 
are the only probabilities which can be offered in support of 
the absence of great masses of water in the central portions. 
For the rest, the climate is variable. 
The following are the chief results which may be deduced 
from the consideration of this subject, viz. :— 
1st, That we must distinguish, in reference to tropical 
rains, two great atmospheric divisions ; the one subjected to 
the trade-winds, and the other to the monsoons. 
2d, That the latter does not admit of absolute deserts, be- 
cause the alternate play of the monsoons always gives rise 
to rains. 
3d, That, nevertheless, the effects of tropical heat, favoured 
by some accessory causes, such as certain breezes, a naturally 
poor soil, and the absence of springs and of rivers, may there 
produce small local deserts, or at least a great general aridity 
(Tehama, Ormus, Beloochistan, Scinde, and Gobi). 
4th, That in the division subject to the trade-winds, the 
low lands of uniform structure, and situated between the 
zones of the intertropical rains and of the subtropical rains, 
do not receive any rain, and are, consequently, characterized 
