ICE IN THE CAVERN OF GRACE-DIEU. 45 



the plain. The entrance of it is 60 feet wide, and about 80 



high. Within its greateft breadth is 133 feet. The ftone that 



forms the rock is calcareous carbonate, in part lamillated. — 



This grotto is diftinguiftied from all others by a very Angular ice is formed ^ 



phenomenon: in fummer ice is conftantly formed in it in large '' 1"/"'?'!^"'''* 

 * . and diminiihcs 



quantities, and this ice diminifhes at the approach of winter, in winter. 



As this natural ice-houfe has been accurately defcribed by Defcribed by 

 Mr. de Croifmare in the Encyclopedic, and feveral other de- ^^^^^^^ writers, 

 fcriptions agreeing with his are to be found in the Memoirs of 

 the Academy of Sciences for 1712, thofe of the Savans Etrangers 

 for 1743, the works of Mr. le Cat and Ravier, and Madame 

 Ganthier's Tour of a French Lady in Switzerland, I (hall con- 

 fine myfelf to a few obfervations, that have efcaped the notice 

 of many of the learned who have vifited it, and combine to 

 explain the formation of the ice in this cavern. 



I vifited it about the end of September, 1791, and then In September, 



found but little ice. My guide, who was accuftomed to con- \^^^il\^J^^^ ^^^ 



du6l travellers to it, informed me, that a month before the ice 



was three times the bulk of what I faw. The perfon who fells A month be- 



refrefliments at Chammars, a public garden at Befan^on, told ^^^ quantity. ' 



me the fame. He faid, that when the winter had proved mild. Ice there in miU 



fo that they were not able to fiil the ice-houfes in the city, ^''^'^'^s* 



he fent in fearch of ice to the cavern of Grace-Dieu, and that 



he chofe for this the warmeft days, becaufe then there was mofi 



ice in the cavern. Meffrs. de Croifmare, le Cat, and Ravier, By feveral au- 



in their accounts, equally atteft, that in fummer the ice is more ph""ties the ice 

 ' T ■' IS molt plentiiul 



abundant. The inhabitants whom I met with on the moun- in fummer. 



tain, and of whom I enquired concerning this fa6t, all told 



the fame thing. Confequently, though the variation of the ice 



is queftioned by Mr. Dunod, quoted in the work of Madame 



Ganthier, I readily admit the exiftence of this phenomenon, 



particularly as I think I can explain it. 



The rock that forms the roof of this grotto is lower than all The rock that 



tbeneighbouring mountains, and even than the furface of the j°JJ^' '^^ ^°° 



plains. Its temperature therefore ought to be mild, like that 



of all fubterraneous caverns, except at the moment when ice 



is accumulated there in abundance. Ten waggons would 



have been fufficient to carry away all I faw, and the air of the The air in it 



grotto did not feel colder to me than the open air. The au- ^l^^ 



thors I have quoted fay, that the cold in it is below 0, I had 



no thermometer, but I can affirm that this alTertion is at lead 



queftionable. 



