58 
of the cave, a long period of inaction as a river channel must 
be allowed for. The number of bats is certainly great, but 
their lease of the premises during which nitre has been thus 
accumulated must have been a long one. 
For convenience of tourists and guides the caverns are 
usually visited by w T hat are called the short or the long 
routes, about and 8 miles long respectively. The short 
route leads for a considerable distance through the main 
cave amid the workings of the saltpetre diggings. This 
main cave, nearly four miles in length, has an average width 
of 60 feet and a height of 40 feet above the present floor, 
which is formed of debris and alluvial deposits considerably 
deep over the real rock floor. Owing to peculiar causes 
in this dry cave, the earth has hardened, and in places the 
guide points out footprints of the oxen used by the miners 
not earlier than the beginning of the century, in clay now 
nearly as hard as rock. The corn-cobs used long ago are 
still undecayed. 
The short route leads visitors from the main cave down 
by a broken opening to a lower range of caverns in the lime- 
stone. These, after passing through various chambers and 
galleries, lead to a series of “domes and potholes.” The 
“ domes,” or portions of the potholes extending upwards, are 
no doubt connected with the funnels of some slough-like 
depressions in the ground above, and have supplied water to 
the various levels of caverns in their turn, while the holes 
having bored some 65 feet lower down, open into the pre- 
sent drainage avenues below. The vertical height of these 
shafts as visible at present is from 200 to 230 feet, and their 
diameter about 25 feet, a size due to the cutting power of 
