- 74 - 
will receive no further contribution until the fall of another 
shower. 
Where forests abound, the case is different. The rain is 
received by a soft and spongy soil, chiefly composed of de- 
cayed leaves, mosses etc. ; it is there preserved from evapora- 
tion hv the shade of the trees, and as it cannot rush down the 
surface of the slope with great velocity, time is given to the 
water to soak well into the ground, which it penetrates to a 
greater of less depth, according to the nature of the soil. The 
water is then collected and drained away gradually, according 
to the arrangement of the subjacent strata, or the formation 
of the rocky bed upon which the vegetable covering and po- 
rous strata lie, and the water ultimately contributes a well re- 
gulated supply to the rivers, often shewing itself as a spring 
at the side of a mountain slope, or even on a plain, at a con- 
siderable distance from its origin, and wherever the course of 
the hidden natural drains may lead it. 
Sometimes the gradual soakage from the higher levels is 
stopped by hollow or flat formations of the ground, where the 
water accumulates and forms marshes or lakes, which serve 
as reservoirs, for the regular supply of constantly flowing- 
streams. 
Mauritius abounds in examples of these processes. 
On the shoulder of the Pouce mountain is a constantly run- 
ning spring, which is due to the gradual draining oft’ of the 
large quantity of moisture received from the atmosphere, by 
the cool summit of the mountain, all the year round. Were 
all the vegetation stripped from the mountain top, it would ne- 
vertheless continue to receive from the atmosphere as much moi- 
sture as hefoi'e ; hut the spring instead of producing a nearly 
regular and a constant flow, would become intermittent, and 
would be sometimes dry and at other times overflowing. 
The Table lands of Yacoas and Savanne also furnish illu- 
strations of a good deal that has been said. These lands on 
account of their elevation * receive a great deal of rain from 
* The approxim. altitude above the sea of Mare aux Vacoas is 1706 feet. 
,, ,, „ of Grand Bassin is ... 1978 „ 
,, „ ,, of Bassin Blanc is ... 
,, „ ,, of the highest part) 
of the ridge between Grand Bassiu and Bassin Blanc j 
1360 
2279 
