Oi'Kjin of J[oiii(t<iui Ildngc.s. — Reade. 277 
than the temperature as the earth is penetrated, what maj- lie 
only semi-solid at 'M) miles may become rigid at greater depths. 
These points, from their nature, are incapable of direct demon- 
stration. l)ut possess a high degree of probability. 
SheU of (Tfcdfest Mohilitj/. 
Although not accepting the hypothesis that there is a fluid zone 
nnder the earths crust, it would follow from the preceding con- 
siderations that the shell occupying the space between the solid 
rigid crust and the compressed rigid nucleus would respond to 
changes of pressure or temperature more readily than either the 
crust or the nucleus. 
Facts of ]*iivsicai> (iEoLocY. 
.^1// iffciit ^fuu iitd ni-R<iiiyts a I'c coinixjsril of i/rraf f/iirLiirssrs of 
SciHmentd ry oiid other Deposits. 
That all great mountain-ranges are composed of great thick- 
nesses of sedimentary and volcanic deposits and igneous intru- 
sions is a fact admitting of demonstration. It is true of tlu' 
Alps, the Andes, the Himalayas*, the Rock}- mountains or North- 
American Cordillera, the Appalachians, the mountains of the 
Caucasus, and the Urals. The .(juestion at once arises in the 
mind, "Is this cause and etfect?" If not. it is a coincidence 
somewhat in the nature of a miracle. 1 f any one example to the 
contrary conld be quoted, the argument of relation would l)e 
weakened, certainly not disposed of, but. so far as j)resent 
knowledge extends, not one can l)e found. 
*Mr. C. S. Middlemiss, iu his extended criticisms on the "Oriiiin of 
Mountain-Ranges" (Memoirs of the Geological Survey of India, vol. 
xxiv, part 2; Physical Geology of the Sub-Himalaya of (Tarliwal and 
Kimiaunl. calls in (juestiou this principle, though it is admitted by nearly 
all geologists since Dr. James Hall established the fact as regards the 
Ajipalachians in IS.")?. Quoting my words in the "Origin," "It is impos- 
sible to point to a range of mountains which lias been built up of old 
denuded rocks,'' he completely misinterprets my meaning, which I had 
thought was plain enough from the Avhole tenor of the work. To give 
an illustration in the form of a prediction, I aver that no mountain- 
range will ever l)e built up out of any portion of the present land-area 
of Europe unless, and until, a l)asin of de|)osition has been established, 
and a thick sedimentary series deposited thereoTi. The old rocks may 
then be forced up along with the new, and form a constituent part of 
sucli a range. Unfortunately, as regards the Hinuxlaya, information is 
meagre; but the granitic axes i)ointed to by Mr. Middlemiss as forming 
the highest peaks of the Himalaya are just what an^ reciuired by \\\y 
theory. 
