AND OF THE OTHER BODIES OF SPACE. 25 



nypothesis, when all the relative phenomena are in har 

 mony with it. This is eminently the case with the nebu- 

 lous hypothesis, for here the associated facts eannot be 

 explained on any other supposition. We have seen rea- 

 son to conclude that the primary condition of matter was 

 that of a diffused mass, in which the component molecules 

 were probably kept apart through the efficacy of heat : 

 that portions of this agglomerated into suns, which threw 

 oft" planets ; that these planets were at first very mueh 

 diffused, but gradually contracted by cooling to their 

 present dimensions. Now as to our own globe, there is a 

 remarkable proof of its having been in a fluid state at the 

 time when it was finally solidifying, in the fact of its be- 

 ing bulged at the equator, the very form which a soft re- 

 volving body takes, and must inevitably take, under the 

 influence of centrifugal force. This bulging makes the 

 equatorial exceed the polar diameter as 230 to 229, which 

 has been demonstrated to be precisely the departure from 

 a correct sphere which might be predicted from a know- 

 ledge of the amount of the mass and the rate of rotation. 

 There is an almost equally distinct memorial of the original 

 high temperature of the materials, in the store of heat which 

 still exists in the interior. The immediate surface of the 

 earth, be it observed, exhibits only the temperature which 

 might be expected to be imparted to such materials, by 

 the heat of the sun. There is a point very short way down, 

 but varying in different climes, where all effects from the 

 sun's rays ceases. Then, however, commences a tempe- 

 rature from an entirely different cause, one which evi- 

 dently has its source in the interior of the earth, and 

 which regularly increases as we descend to greater and 

 greater depths, the rate of increment being about one de- 

 gree Fahrenheit for every sixty feet ; and of this high 

 temperature there are other evidences in the phenomena 

 of volcanoes and thermal springs, as well as in what is 

 ascertained with regard to the density of the entire mass 

 of the earth. This, it will be remembered, is four and a 

 half times the weight of water ; but the actual weight ot 

 the principal solid substances composing the outer crust 

 is as two and a half times the weight of water ; and this, 

 we know, if the globe were solid and cold, should increase 

 vastly towards the centre, water acquiring the density ot 

 quicksilver at 362 miles below the surface, and other 

 things m proportion, and these densities becoming much 

 3 



