290 On the Elevation of Mountain Ranges. 



Art. XV. — On the Elevation of Mountain Ranges. 



It is an old theory, that the lower rock formations are more easily 

 determined than the upper and more recent ; it being sufficient to 

 examine a small portion of territory, in order to consider the remain- 

 der analogous in age and character. Those who still advance (not 

 to say maintain) the opinion, and believe in good faith that a part, 

 for instance, of the northern extremity of the Rocky Mountains is an 

 index for their whole extent, even to the extreme south, are cer- 

 tainly far behind the age in the investigations of a science where ad- 

 vancements are as rapid as in geology. That no such sure analo- 

 gies are presented appears probable from hypothesis, and more than 

 probable from observation. European geologists recognize within 

 the small extent of the Alps not less than three, and in the Pyrenees 

 four distinct classes. The writer will now make a few remarks on 

 causes which might produce so seeming a correspondence with so 

 wide an actual difference. 



If the earth contain, as is probable, a series of immense galvanic 

 batteries, producing the results of electric and magnetic phenomena, 

 the identity of the element being inferred ; then it may be assumed 

 that this principle, acting by such vast machinery, and on so grand 

 a scale, is adequate to the explanation required. And this power, 

 which extends with variations from south to north, and proves the 

 accumulation offerees to be in that direction, might, in one age, by 

 a sudden expansion of elements, throw up the precipitous barrier 

 mountains of Chili ; and in another, acting on different combinations, 

 produce the gradual swell of the crust above in the rise from the 

 valley of the Mississippi, to the summits of the same range in our 

 latitudes. Thus it is not difficult to conceive that an extensive and 

 continuous mountain range may present characteristics entirely dis- 

 similar. That the accumulation of forces is in the direction of the 

 line of no variation, and not simply at the point beneath the mag- 

 netic pole, is manifest, in as much as the attraction is towards the 

 line, and not directly towards the pole. Thus in 1813, the declina- 

 tion of the needle at New Orleans was 8° east, and at Philadelphia 

 2° 27' west. If it be supposed that the needles were directed to 

 some point of attraction, it would necessarily be where these lines 

 produced will meet, which places the magnetic pole much too far 

 south. Therefore it is evident that the attracting power lay between 



