SPELEOLOGY, OR CAVE EXPLORATION. 259 



exploration in a dry season might reveal many very interesting 

 chambers. 



In the cave of Rabanel, the first well, which ends in a talus of 

 fallen stones, furnishes an instance of a vertical fissure grafted, if 

 we may use the word, upon an interior grotto that already existed. 

 A stream runs through this grotto which falls into a second well 

 twenty-six metres, and is then lost in smaller passages so nearly 

 stopped up with earth that we were not able to follow it through 

 its course of about a mile till it comes out at the Brissac spring. 



The cave of Trebiciano, in Istria, near Trieste, the deepest 

 known, has a total depth of more than a thousand feet. It is not, 

 however, entirely natural, but is composed of numerous vertical 

 fissures which lead, at about eight hundred and fifty feet below the 

 surface, to a large cavern, at the bottom of which flows the subter- 

 ranean river Recca. The fissures do not naturally communicate 

 directly with one another, but the engineer Lindner was commis- 

 sioned in 1840-'41 by the city of Trieste to construct for the mu- 

 nicipality a supply of potable water from the underground streams, 

 and after eleven months of labor made artificial connections between 

 the different parts of the chasm. 



These vertical pits are formed by the wearing down, from the 

 top, by the waters which become ingulfed in them. This mode of 

 their formation was demonstrated to me in 1895, when I was in 

 Great Britain under a commission from the French Minister of In- 

 struction. I then explored several caves in which the rivers were 

 still running, and satisfied myself that the pits were simply absorbing 

 wells. Such wells are not effective now in southern France and 

 Austria, but in northern Europe, where rain is more abundant, they 

 are still operative. I found the plainest evidence of this fact in 

 Yorkshire, at the Gaping Ghyll, Ingleborough, where a river pre- 

 cipitates itself at one leap one hundred metres under the earth. 

 English investigators and travelers had tried without success to de- 

 scend into it in 1845, 1870, and 1894, having conquered only about 

 one hundred and ninety-five feet of its total depth of two hundred 

 and twenty-nine feet. It took me twenty-five minutes to go down 

 upon a rope ladder which was suspended in the midst of the cascade. 

 Fortunately, the pit had the daylight to the very bottom — a won- 

 derful spectacle, compensating me for all my trouble and the long 

 douche bath which greeted me at the end of the descent, where 

 stretched an immense Roman nave nearly five hundred feet long, 

 eighty feet wide, and ninety feet high, without any sustaining pillar. 

 From the middle of the roof of this colossal cavern fell the cascade 

 in a great nimbus of vapor and light — a wonderful fantastic scene, 

 such as Gustave Dore or Jules Verne could never have imagined. 



