NATURAL PHILOSOPHY.

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situation where cold is most felt, in a fact recorded by anauthor to whom our obligations have been often due. M.P. J. Von Strahlenberg , in his Historio-geographical De-scription of the North and North-eastern parts of Asia andEurope , has thus described the effects he experienced ina cave in Siberia .

“ In the year 1722, in the month of February, going ina sledge on the river Jenisei , I observed such a cave,” ashe had previously described, “ between the two cities ofAbakan and Crasnoyahr. The banks of the river are in thisplace a steep rock as high as any church-steeple, in themiddle of which there appeared an opening about fortyfathoms above the surface of the water. The entrance intothis cave is about five fathoms wide, and near fifteen fathomsin height. I went into this place, and advanced upwardsinto the rock as far as I could conveniently, I think aboutthirty fathoms; but finding the passage darker, and notwith-standing it was in the depth of winter, and that day beingbesides a terribly cold one, there came from this cavity sowarm a vapour that it made me sweat, and discouraged meas well as my fellow traveller from venturing any further.We had a great deal of trouble to come at the entrancefrom the bottom ; for this rock is very steep, and was atthat time covered near six feet thick with snow, whichbeing pretty compact, was the only means by which wecould get up by fixing our feet into it: however, we couldnot help sliding sometimes a good way down again. TheSwedish boy, whom I have had occasion to mention above,was with me in this place, and he with the Tartar who drovethe sledge, both advanced higher, almost to the top of therock; where they met with another opening, within whichthey found several pieces of old household goods, and thisgave us room to believe, that formerly it must have beeninhabited. This confirmed the opinion which myself andfellow traveller, who was a Russian dragoon,” (our authorwas a prisoner of war), “ conceived when we were in thecave, viz. that there must be a communication between theopening we entered and some other cavity; because, smo-king a pipe whilst we were in it, we did not perceive thatthe smoke came back towards the entrance of the cave.That which I thought most observable in that part of thecave I was in, (besides some dead birds, such as that sortwhich the Germans call silk-tails, in Latin , garrulus Bohe-micns, and two kinds of bats with long and narrow ears,)was a vast number of icicles about the top of the entrance,formed by the concourse of the warm vapours from within

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