262 ON THE FORMATION OF ROCKS. (June, 



entirely ignorant; few of our mines penetrate deeper than 

 one fifty thousandth part of the earth's diameter under 

 the surface, and none of them go beyond one twenty-five 

 thousandth part of that diameter: it would appear, there- 

 fore, that any mere supposition concerning the actual and 

 present state, or the nature of those substances ^vhich 

 form the interior of the earth, is unsupported as yet by any 

 reasonable analogy; and that all conjectures concerning 

 former changes, partial or total, in the nature and struc- 

 ture of those substances, are removed still farther from 

 any thing analogous in our present state of knowledge. 



The earth being flattened at the poles, does not ne- 

 cessarily imply its former fluidity; we may be permitted 

 to doubt the analogy between our experiments on bodies 

 moving in our atmosphere, and the earth's motion in 

 space: our total ignorance of the nature of the fluid which 

 occupies what is usually called space, tends to render the 

 analogy inconclusive. 



May not the mode of casting patent shot be consider- 

 ed as an experiment on the form which liquid bodies 

 would take by a rotatory motion? A .drop of melted lead 

 let fall from the height of two hundred feet is completely 

 globular, and not flattened at the poles; the lead might 

 be thrown with force from the top of the tower, which 

 would imitate the centrifugal force, as gravitation does 

 the centripetal force, and make the experiment more 

 analogous. 



The supposition , that the earth was in a fluid state 

 when it took its present form, leads to the supposition 

 that it was always so; and that fluidity w as the original 

 state of the earth, kept so by all the general laws and or- 

 der of nature, all of vvhich general order and laws of na- 



