GENERAL TEMPERATURE. 
271 
We have just seen that, in the Cueva del Gruaeharo, 
the Mater of the river is nearly 2° colder than the am- 
bient air of the cavern. The water, whether in -filtering 
through the roehs, or in running over stony beds, doubt- 
less imbibes the temperature of these beds. The air 
contained in the grotto, on the contrary, is not in repose ; 
it communicates with the external atmosphere. Though 
under the torrid zone, the changes of the external tem- 
perature are exceedingly trifling, currents are formed, which 
modify periodically the internal air. It is consequently 
the temperature of the waters, that of 16"S' J , which we 
might look upon as the temperature of the earth in those 
mountains, if we were sure that the waters do not descend 
rapidly from more elevated neighbouring mountains. 
It follows from these observations, that when we can- 
not obtain results perfectly exact, wo find at least under 
each zone certain numbers which indicate the maximum 
and minimum. At Caripe, in the equinoctial zone, at an 
elevation of 500 toises, the mean temperature of the globe 
is not below 10'8°, which was the degree indicated by the 
water of the subterranean river. We ean even prove that 
this temperature of the globe is not above lffi, since the air 
of the cavern, in the month of September, was found to he at 
18 - 7°. As the mean temperature of the atmosphere, in the 
hottest month, does not exceed 19-5 0 ,* it is probable that a 
thermometer in the grotto would not rise higher than 19° at 
any season of the year. 
* The mean temperature of the month of September at Caripe is 
18'5°; and on the coast of Cumana, where we had opportunities of 
making numerous observations, the mean heat of the warmest months 
differs only 1*8° from that of the coldest. 
