Lecture on the Formation of Mountains. By Captain Hurron, F.G.S.,C.M.Z.8. 
[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- 
edge of facts—which are the objects of inquiry to the natural philosopher.”—Sir J. HERSCHEL, 
Tue 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 proved, 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 I have to say quite clear tu 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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