344 THB BEASON "WHY. 



" His going forth is from the end of the heaven, and his circuit unto the ends of 

 it ; and there is nothing hid from the heat thereof." PSALM nx. 



New World, it has diffused itself over it, from the 50th parallel north as far as 

 Patagonia. Originally the cat was not known in America, nor in any part of 

 Oceanica ; but it has now spread into almost every country of the globe. Among 

 animals entirely wild, the most extensively diffused, are the fox, hare, squirrel, 

 and ermine ; but the species are different in every region of the world ; nor is 

 there perhaps one example to be found of a species perfectly identical naturally 

 existing in distant localities of the earth. 



Respecting the internal constitution and Jieut of the earth, differences of 

 opinion, and some very wild speculation have existed. We find in Huinboldt's 

 " Cosmos " the following remarks : 



1335. " It has been computed at what depths liquid and even gaseous 

 substances, from the pressure of their own superimposed strata, would attain 

 a density exceeding that of platinum, or of iridium ; and in order to bring the 

 actual degree of ellipticity, which was known within very narrow limits, into 

 harmony with the hypothesis of the infinite compressibility of matter, Leslie 

 conceived the interior of the Earth to be a hollow sphere, filled with "an 

 imponderable fluid of enormous expansive force." Such rash and arbitrary 

 conjectures have given rise, in wholly unscientific circles, to still more fantastic 

 notions. The hollow sphere has been peopled with plants and animals, on 

 which two small subterranean revolving planets, Pluto and Proserpine, were 

 supposed to shed a mild light. A constantly uniform temperature is supposed 

 to prevail in these inner regions, and the air being rendered self-luminous by 

 compression, might well render the planets of this lower world unnecessary. 

 Near the north pole, in 82 deg. of latitude, an enormous opening is imagined, 

 from which the polar light visible in Aurora streams forth, and by which a 

 descent into the hollow sphere may be made. Sir Humphry Davy and myself 

 were repeatedly and publicly invited by Captain Symmes to undertake this 

 subterranean expedition ; so powerful is the morbid inclination of men to lill 

 unseen spaces with shapes of wonder, regardless of the counter-evidence of 

 well-established facts, or universally recognised natural laws. Even the 

 celebrated Halley, at the end of the 17th century, hollowed out the earth in his 

 magnetic speculations ; a freely rotating subterranean nucleus was supposed to 

 occasion, by its varying positions, the diurnal and annual changes of the 

 magnetic declination. Is has been attempted in our own day, in tedious 

 earnest, to invest with a scientific garb that which, in the pages of the 

 ingenious Holberg, was an amusing fiction." 



The following are among the speculations which Humboldt thus severely but 

 justly condemns . 



" The increase of temperature observed is about 1 deg. Fahr. for every fifteen 

 yards of descent. In all probability, however, the increase will be found to be 

 in a geometrical progression as investigation is extended; in which case the 

 present crust will be found to be much thinner than we have calculated it to 

 be. And should this be found to be correct, the igneous theory will become a 

 subject of much more importance, in a geological point of view, than we are at 

 present disposed to consider it. Taking, then, as correct, the present observed 

 rate of increase, the temperature would be as follows : 



Water will boil at the depth of 2,430 yards. 

 Lead molts at the depth of 8,400 yards. 

 There is red heat at the dopth of 7 miles. 

 Gold melts at 21 miles. 

 Cast iron at 7i miles. 

 Soft iron at 97 miles. 



And at the depth of 100 miles there is a temperature equal to the greatest 

 artificial heat yet observed r a temperature capable of fusing platina, porcelain, 

 and indeed every refractory substance we are acquainted with. These tempera- 

 tures are calculated from Guyton Morveau's corrected scale of Wedgwood's 

 pyrometer ; and if we adopt them, we find that the earth id fluid at tho deptfc 



