166 Notices of Memoirs — Sutton, on Mountains. 



more powerful for denuding on the west, where more rain falls, and 

 in glacial periods there would no doubt have been more snow. May 

 not the explanation of these facts be, that the western side has gone 

 up higher within some late period ; so that although denudation has 

 gone on, perhaps even more rapidly, upon its hills, they nevertheless 

 remain more lofty, because the altitude requiring to be reduced since 

 that time has been more considerable ? 



VI. — Supplementary Note on Minerals found in Somersetshire.' 

 By Spencer George Perceval. 



AGATES are found abundantly in Somersetshire. Dr. Buckland 

 mentions their occurrence at Sandford, near Banwell, Worle, 

 and Clevedon. Trans. Geol. Soc, ser. 2, vol. iii., p. 421. See also 

 Sowerby's British Mineralogy, vol. v., 1817, p. 213. 



Copper occurs in a conglomerate quarry behind the village of 

 Alcombe, near Minehead. 



Fluor spar occurs at Clifton, in the Great Quarry on the Glou- 

 cestershire side of the Avon, in the form of small purple cubes, in 

 cavities of the Mountain Limestone, lined with crystals of Calcite 

 and occasionally of Pearl sjDar : also on the Somersetshire side of the 

 Avon section. 



Bitumen also occurs (liquid and consolidated) in adjoining cavities 

 in the Moimtain Limestone. 



I. — On the Formation of Mountains.^ 



By Captain Huttgn, F.G.S., C.M.Z.S, 



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

 not the mere knowledge of facts — which are the objects of inquiry to the natural 

 philosopher." — Sir J. Herschel. 



ryiHE formation of mountains does not very well describe the subject 

 _L 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 

 undulating, 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 centurj'-, 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 extra- 

 ordinary phenomena of nature with which science has made us 



^ See list by H. B. Woodward in Geol. Mag., Vol. IX., March, 1872. 

 2 Substance of a lecture delivered in the Colonial Museum, Wellington, New 

 Zealand, 13th November, 1872, 



