ColJ Wliuls luhich ijjiie out of the Earth. 229 



liave frequently been compared. For, if we compare the effefts of the nitric acid on thefe 

 concretions, the foregoing obfcrvations flievv that its action upon them is very different from 

 its action upon camphor. 



IX. 



On the Ccld Winds which ijfue otit of the Earth. By Prof-Jfor De SauSSUSE and others; 

 •with Obfervations. 



X N the fifth volume of De SaulTure's Voyages dans les Alpes, page 342, lately publlflied, the 

 author, after having afcertained by experiment that the water at the bottom of the Alpine 

 Lakes is much colder than temperate, namely, about 4 degrees of Reaumur, while that of the 

 furface indicated about 15°, whereas the temperature of the water at 886 feet and at j8oo 

 feet depth in the Gulph of Genoa, near the land, proved to be above temperate, namely, 10,6 

 degrees, while at the fujfface the heat was i6| degrees, proceeds to make remarks on a 

 phenomenon probably of the fame nature, that there are many fubterraneous cavities out 

 of which winds iflue, which are colder than the mean temperature of the earth. The 

 former effects are confidered by this author as very difficult to be accounted for ; and 

 indeed they appear to depend on the principle of the almoft perfeft non-condu£ting power 

 of fluids with regard to heat, which has fcarcely, if at all, been treated by any author but 

 Count Rumford in his feventh efiay, publifhed a few days ago. The latter he thinks- 

 may more eafdy be explained. I fhall here relate the fadls by a tranflation nearly clofe, 

 and afterwards give the fubftance of his reafonings, with fuch remarks as may prefentt 

 themfelves. 



He begins his account with the caves of Mont Teflaceo near Rome, which were th& 

 fnft that fixed the attention of an accurate obferver. The Abbe Nollet obferved them irt 

 his travels into Italy*, and found their temperature was pj degrees on the 9th of 

 September 1749, in the afternoon, while the thermometer in the open air ftood at 18 

 degrees ; and he remarks with reafon, that their coolnefs is fo much the more aftonilhing^ 

 as they are not deep ; that the entrance has fcarcely any defcent, and that the fun fiiines 

 for the greateft part of the day upon the door of the entrance. 



M. De Sauflurc found them cooler than the Abbe Nollet did, though he vifited them in 

 hotter weather ; the reafon of which, as he remarks, may be deduced from the explanation 

 of the phenomenon. On the firft of July 1773, the external air in the (hade was at 20-| 

 degrees ; that of one of the caves was at 8 ; of another at jj; and of a third at 5^. 

 Thefe caves are made in the fide of the mountain, and occupy nearly its whole circum- 

 ference. Thofe he entered were on the weft fide. The walls at the bottom have perfo- 

 rations through which the cold air enters. 



The air itfelf comes through the interftices left between tlic pieces of broken urns, 

 amphorx, and other vefllls of pottery of which this fmall mountain appears to be entirely 

 compofcd. He went to its fummit, which is not above two or three hundred feet in 



■* Anvil, dcs Scltiices, 17^9, page 486. 

 4 - height. 



