l^'^t! rill Alinriiii II ( 1 1 iiliK/tst . NdNciiiliiT, IS'.tl 
to fliilioiMtc \vli:il could lie jiisl.lv ("illcil :i tlicofv of MouiitMih- 
liiiildiiiii'. 'I'lu'V ij.:i\i' to llu' world sonic t'niitf'ul sii<i<:('stioiis. and 
iKMitc I'ciisouiim' tlicrcoii. which hnvc liccu of coiisidcrahlc use to 
:i succession of speculators in <i'eol()i>ical physics, and to myself 
anion;j,the wsV"' . One of the most frecpieut ly ur<i"ed ol)jections 
to my theory is the supjjosi'd inade(|uacv of expansion Ijy rise of 
temperature to account for tlu' excessive foldinij,- some monnlain- 
clinins iiave undergone, linear expansion oidy licinii' considered. 
]My reply to this is that even linear expansion alone |)laces at our 
disposal more lati-rai movement than any otlu'r theory. It is 
true that tlntsc speculators wiio have invoked tansxential thrust 
throuiih the assumed shrinUiiiii- of the earth's inicleus. have had 
at their command any amount of hitcral movement their imagina- 
tion liUed to draw upon, hence the simplicity and success of the 
theory — for a time. It lias, howi'ver, l)een shown pretty oloai'Iy 
that the liank upon which these checpies have been drawn is one 
of very limited lialiilityt. and (piite une(pial to honorinu' them. 
I'rof. Hutton. in his very able address toSi'ction (' of the Mel- 
bourne meeting of the Austndasian Association for the Advance- 
ment of Science, gives an excellent n'smiu' of the various 
hvpotheses that have been suggested to account for mountain- 
building. 1 contidently a))}H'al to his description to show that, 
omitting the theory of secidar contrtiction of the earth's nncleijs, 
Avhich he disposes of very etfectually. none of the suggestions, 
tlicories. or hyi)otheses except the one I su|)port provides any 
lateral mo\cment other than that due to intrusions of molten 
rock. 
Trof. Hutton. in his dcscinpt ion of my theory, doubtless given 
in the greatest good laitli. leaves out what arc in my view sonu> of 
its vital and essential j)ortions. I gave as an illustration the 
cubical ex|)ansion of an area of rock 500 X •">"*• X -'• miles, and 
sliowed that it would, if raised 1.000° Fahr.. have an ctfective 
increase of bulk of 7)'2.\'.>') cubic miles|. I'rof. Hutton seems to 
assunu' that this is the Al,l'n.\ and O.mko.v of my theory the 
bcuinning and the v\](\. I cannot l»ut think it strange th:it he 
*Until after my work was published I had read uothiug of this but 
what was contained in Lyell's "Principles" and letters, and Babbage's 
paper, read l»efore the (ioological Society in 1834, nor had T read Scrope'?* 
views. 
+See Ilutton's examination of this tlieory in the Address referred to. 
+ "Origin of Mountain-Ranges,"' p. 11(5. 
