parallel to its axis, niul the niuiie will receive another accession 
of hnlk. 
Tims we see that the ett'ect of alternation of tenii)eratiire 
in the earths crust leading to the establishment of mountain- 
chains is cumulative. This cumulative effect of small alterna- 
tions of temperature may he seen in the ridging-up of any old 
lead gutter, lead flat, or lead-lined hath or sink. Tt has been 
likened to a --rachet " movement, which is not an inai)t illustra- 
tion if taken with the necessary (puilitications. 
Effects of contraction. — Nok.mai. faci.tinu. 
Normal faults, that is faults tluit hade to the downthrow, are 
the result of contraction, and are posterior t(j the lirst plica- 
tion. An}' section of a mountain-range traversed liy normal 
faults shows the folds sheared in a way that proves this. Nor- 
mal faulting is. however, most prevalent in the less disturljed 
strata that flank a range. The mountain-range pushed up by 
successive lateral thrusts (jr recurrent expansions acting over a 
great length of time and the folds thrown back and further com- 
pressed l)y the cores of gneiss and granite intruded into them. 
becomes a solid mass which cannot be drawn back by contraction. 
Contraction therefore has its maximum effect on the more hori- 
zontal deposits that flank the lange. and I'xtend foi- coiisidei'alile 
distances on either side. 
As the crust of the earth must remain solid, the conditioa is 
satisfied by shearing and wedging-up by gravitation. — otherwise 
by normal faulting. Contraction of igneous masses beneath may 
induce this faulting in some cases, liut it is not a necessary condi- 
tion, ("ultical contraction of the solid crust is sutliciciit. 
Aiisiriix to sniiir n/ijtcf iaiis. 
The oliject of this outline of my theory is to focus its salient 
points, as many of my critics for some reason or otlici' ha\'e failed 
to grasp them. What tiiey critcise is frecpiently not my theorv. 
but some rather vagut' notion called tlic • •IIerschel-H;d)lta<>:e" 
theorv. What is exactly covered liy this desi-riptioii I have a 
difliculty in ascei'taining. ()n tlie otiici- hand, one writer calls 
Mr. (). Kisher's theorv. with wliicli mine has no analogy, the 
••Tlerschel-lJabl)age" theorv. I trust I shall give no olfenci- liv 
repudiating this labelling and claiming the tlieoiy as my own. 
Neither lierschel. Scroi)e. nor Haljbage ever advanced so far as 
