116 Things not generally Known. 



of the Kirghis, is employed by the inhabitants as a cellar. It 

 has the very remarkable property of being so intensely cold 

 during the hottest summers as to be then filled with ice, which 

 disappearing with cold weather, is entirely gone in winter, when 

 all the country is clad in snow. The roof is hung with ever- 

 dripping solid icicles, and the floor may be called a stalagmite 

 of ice and frozen earth. " If," says Sir R. Murchison, " as we 

 were assured, the cold is greatest when the external air is hottest 

 and driest, that the fall of rain and a moist atmosphere produce 

 some diminution of the cold in the cave, and that upon the set- 

 ting-in of winter the ice disappears entirely, then indeed the 

 problem is very curious." The peasants assert that in winter 

 they could sleep in the cave without their sheepskins. 



INTERIOR TEMPERATURE OF THE EARTH : CENTRAL HEAT. 



By the observed temperature of mines, and that at the bot- 

 tom of artesian wells, it has been established that the rate at 

 which such temperature increases as we descend varies consi- 

 derably in different localities, where the depths are compara- 

 tively small ; Hbut where the depths are great, we find a much 

 nearer approximation to a common rate of increase, which, as 

 determined by the best observation in the deepest mines, shafts, 

 and artesian wells in Western Europe, is very nearly 1 F. for 

 an increase in depth of fifty feet* W. Hopkins, M.A., F.R.S. 



Humboldt states that, according to tolerably coincident 

 experiments in artesian wells, it has been shown that the heat 

 increases on an average about 1 for every 54*5 feet. If this 

 increase can be reduced to arithmetical relations, it will follow 

 that a stratum of granite would be in a state of fusion at a 

 depth of nearly twenty-one geographical miles, or between 

 four and five times the elevation of the highest summit of the 

 Himalaya. 



The following is the opinion of Professor Silliman : 

 That the whole interior portion of the earth, or at least a great part 

 of it, is an ocean of melted rock, agitated by violent winds, though I 

 dare not affirm it, is still rendered highly probable by the phenomena 

 of volcanoes. The facts connected with their eruption have been ascer- 

 tained and placed beyond a doubt. How, then, are they to be accounted 

 for ? The theory prevalent some years since, that they are caused by 

 the combustion of immense coal-beds, is puerile and now entirely aban- 

 doned. All the coal in the world could not afford fuel enough for one 

 of the tremendous eruptions of Vesuvius. 



This observed increase of temperature in descending be- 

 neath the earth's surface suggested the notion of a central 

 incandescent nucleus still remaining in a state of fluidity from 

 its elevated temperature. Hence the theory that the whole 

 mass of the earth was formerly a molten fluid mass, the exte- 

 rior portion of which, to some unknown depth, has assumed 



