Lecture on the Formation of Mountains. By Captain Hutton, F.G.S., C.M.Z.S. 



[Substance of a lecture delivered in the Colonial Museum, Wellington, 13th November, 1872.] 



" We must never forget that it is principles, and not phenomena— the interpretation, not the mere know- 

 ledge of facts — which are the objects of inquiry to the natural philosopher."— Sir J. Herschel. 



The formation of mountains does not very well describe the subject on which. 

 I propose to lecture to night, for, strictly speaking, mountains are formed by 

 rain and snow sculpturing and grooving what would otherwise have been 

 table lands, or the highest portions of the undulations of the earth's surface ; 

 but on this subject I do not mean to touch. I propose to deal with the 

 undulations themselves, out of which mountains are carved by the rain. 



It is well known that the solid surface of the globe is uneven and undulat- 

 ing, that the lower portions are covered by the ocean, while the higher are 

 called the land, and it has also been j)roved, by observations extending over 

 nearly a century, that these undulations have changed in form and position 

 over and over again, and that changes are still going on. That the solid 

 surface of the earth should heave and quiver, and sway up and down, is one of 

 the most extraordinary phenomena of nature with which science has made us 

 acquainted, and it is one which has never yet received a satisfactory explana- 

 tion. I hope, however, to be able to show you that it is but the necessary 

 effect of causes which we know from observation to be constantly going on on 

 the surface, combined with the conduction outwards of the interior heat of the 

 earth. 



In order to make what T have to say quite clear to you, I must first briefly 

 refer to some general considerations on the interior of the earth. Fortunately, 

 it will not be necessary for me to enter into the hotly disputed question as to 

 whether it is fluid or solid, for this is immaterial to the views that I have to 

 advance ; all that is necessary being that the interior is very hot. This is 

 allowed, I believe, by all scientific men, the proof resting principally on the 

 facts that we know from observations, wherever they have been made, that the 

 temperature actually does rise as we descend, at an average rate of about 

 1° Fahr. for every fifty feet, and that the density of the earth is so small, 

 not much more than twice that of the ordinary rocks of the surface, that 

 there must be some expansive force in the interior sufficiently powerful to 

 balance in a great measure the enormous pressure to which the interior of 

 the earth would be subjected. Assuming then that the interior of the 

 earth is intensely heated, and that the temperature, for a depth say of fifty 

 miles from the surface, increases at the rate of 1° Fahr. for each fifty feet, it 

 necessarily follows that the outer shell, or " crust " as it is commonly called, to 



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