334 On the Mammoth Cave of Kentucky. 
below the hotel, and the level of the rivers of the cave to be 
the same as that of Green river with which the subterranean 
rivers or lakes rise and fall in times of flood; so that there is no 
doubt of a connection existing between Green river and these 
terious silence many miles from.the entrance, and at least 300 
feet from the upper surface.. Unfortunately our party was unpro- 
vided with barometers, and the measurement of Dr. Locke re- 
mains therefore as the only evidence we have of the relative 
levels of these subterranean waters and Green river. 
One atmospheric phenomenon attracted our attention and tasked 
our ingenuity for a satisfactory explanation. I will mention the 
fact and our solution of it. If the external air has a temperature 
If the air without has a temperature of 59°-60° no current is 
observed and the flame of a lamp held in a favorable position 1n- 
dicates none. It immediately occurred to me that there must be 
two currents, one above of warmer air, passing inward, and one 
below of colder air passing outward, and the reverse, but experi 
ment soon satisfied me that this was not the case. Only one 
current could be discovered, and on inquiry of the very intelli- 
gent guide, ‘Stephen,’ who is well known for his remarkable 
powers to all who have been at the cave, I found that this phe- 
nomenon had attracted his attention, and that he was satisfied 
from many observations that only one current existed and that 
this flowed owt when the external air was above 60° and inward 
when this was below 60°. Going in, one day at noon, we fount 
the outward blast very strong: we prolonged our stay until 
past midnight; meanwhile a storm of rain accompanied by light- 
ning had come up, and at 3 a. m. when we again emerged, the 
temperature outside had fallen to 50°, and the inward gale blew 
So strongly as to extinguish our lights several hundred yards 
from the mouth. In fact the guide told us, when more than two 
Miles in the cave, that a change had taken place in the outer alr, 
and that we should probably find a storm raging without. His 
accustomed senses detected the gentle current inward which we 
did not notice at so great a distance, and he perceived, as he after- 
ward told us, a change of level in the subterranean rivers, since — 
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