46 



Dcfcilption of 

 the cavern. 



Clear water 

 burfts through 

 the rocks and 

 falls into a bafon 

 of ice. 



The grotto is 

 covered by 

 faufliy trees. 



The ground is 

 cooled by the 

 evaporation in 

 funruner, 



which does not 

 take place in 

 winter. 



The trees over 

 the entrance 

 being cut down, 

 lefs ice was 

 formed. 



The entrance 

 was partly clofed 

 up by a wall. 



by which the 

 ice was dimi- 

 fiinied. 



ICE IN THE CAVERN OP GRACE DIEIT. 



A juft idea of the fituation of the cavern is fufficient to fliev^f 

 in wliat manner the water percolates the flrata of rock, and 

 falls perpetually from the roof. The cavern is farrounded by 

 thickly wooded mountains, and from one of the neareft rocks 

 r a flics a torrent, that forms three cafcades, and turns feverai 

 mills. But what is remarkable is, that the water filtering into 

 the cavern does not freeze as it falls: it is received into a bafin 

 of two or three feet diameter formed in the ice, and remains 

 fluid on a level with the fides of the bafin. I drank fome of 

 this water, which did not feem to me very cold. It was per- 

 fei^ly clear and good. 



I obferved, that the grotto is not only furrounded by wood 

 on all fides, but that it is covered by a number of the moft 

 beautiful beech, and bufliy chefnut trees. Thefe deny all ac- 

 cefs to the rays of the fun, and always preferve a cool damp 

 air round the cavern. This fliade however would not be fuf- 

 ficient to pro'duce an icy air, but the leaves of thefe trees are fo 

 many organs of perfpiration, that pour into the atmofphere the 

 raoifture which exhales from their vefl^els, and that has been 

 pumped up by their roots. This evaporating water cannot 

 pafs from the flate of a fluid to that of a gas, without abforb- 

 ing a large quantity of caloric: the ground therefore is conti- 

 nually cooled by the evaporation the trees produce. In winter 

 the warmth of the fun no longer draws up moiflure; the leaves, 

 which botanifts confidcr as real lungs, have difcontinued their 

 organic adion; and the fame evaporation no longer exi lis. 

 The temperature of the cavern then changes, and approaches 

 that of fubterranean places and grottos in general. Several 

 fa6ls ferve to confirm this theory, and to prove, that the cold 

 produced in the cavern of Graqe-Dieu is entirely owing to the 

 fpeedy evaporation of the furrounding moifture. 



Mr. Ravier, fecretary to the bifliop of Bellay, fays, that in 

 1724, the entrance of the grotto was overfliadowed by large 

 buftiy trees, that thefe were cut down, and that the quantity 

 of ice afterwards formed has been lefs. 



He alio reports, that Mr. de Vanolles, intendant of the pro- 

 vince, defirous of preferving this natural curiofity, clofed up 

 the grotto by a wall twenty feet high, with a fmall door, the 

 key of which was entruft^d to the bailiffs of the village, with 

 a charge, that, no one fhould be fufi'ered to enter Tor the pur- 

 pofe of carrying away the ice. But this precaution produced 



4 an 



