1907] AND CONTRACTION OF THE EARTH. 289 



the continents are large areas, and altogether cover more than one 

 fourth of the total surface of the globe ; yet the volcanoes and world- 

 shaking earthquakes are confined to the neighborhood of the oceans 

 or other large bodies of water. 



5. It clearly follows therefore that the agitating vapor does not 

 come from the central magma of the globe, but must come from the 

 secular leakage of the ocean bottoms. This is unmistakably indi- 

 cated by the most overwhelming evidence of nature.^ 



^ Newton's rules of reasoning in natural philosophy should be borne in 

 mind here : 



Rule I. " We are to admit no more causes of natural things, than such 

 as are both true and suMcient to explain their appearances." 



" To this purpose the philosophers say, that Nature does nothing in vain, 

 and more is in vain, when less will serve; for Nature is pleased with sim- 

 plicity and affects not the pomp of superfluous causes." 



Rule II. " Therefore to the same natural effects we must, so far as 

 possible, assign the same causes." 



"As to respiration in a man, and in a breast; the descent of stones in 

 Europe and in America; the light of our culinary fire and of the sun; the 

 reflection of light in the earth, and in the planets." 



Rule III. " The qualities of bodies, which admit neither intension nor 

 remission of degrees, and which are found to belong to all bodies within the 

 reach of our experiments, are to be esteemed the universal qualities of all 

 bodies whatsoever." 



Newton's explanation of this rule is too long to be quoted here; but it 

 is worthy of the most careful study. 



Rule IV. "In experimental philosophy we are to look upon proposi- 

 tions collected by general induction from phenomena as accurately or very 

 nearly true, notwithstanding any contrary hypotheses that may be imagined, 

 till such time as other phenomena occur, by which they may either be made 

 more accurate, or liable to exceptions." 



" This rule we must follow that the argument of induction may not be 

 evaded by hypotheses." 



In the investigation of the physics of the earth involving many hypotheses 

 of very unequal weight this last rule acquires special importance. If there- 

 fore some trifling details are not yet explained or understood we must not 

 on that account reject the cause gathered by a general induction of all the 

 related phenomena of the globe. On the contrary we must adhere to the cause 

 " as accurately or very nearly true, notwithstanding any contrary hypotheses 

 that may be imagined, till such time as other phenomena occur, by which they 

 may either be made more accurate, or liable to exceptions," in order that the 

 " argument of induction may not be evaded by hypotheses." In his expla- 

 nations of Rule III. Newton remarks: "We certainly are not to relinquish 

 the evidence of experiments for the sake of dreams and vain fictions of our 

 own devising; nor are we to recede from the analogy of Nature which uses 

 to be simple, and always consonant to itself." 



