46 
THE MED ITERIi AN E A T NATURALIST 
Japed it is only what might have been predicated 
of them. A true theory must take account of all 
the phenomena found in connection with the effect 
it professes to explain. How, then, could this 
have been done of the crust oi the earth before 
the nature of that crust had been approximately 
ascertained? 
The origin of Mountain Ranges is a subject 
which hitherto has not received much systematic 
study. It is true that several eminent men have 
made valuable suggestions as to the forces which 
they think have been left in a very crude and unfi- 
nished state, and the proofs offered not being of a 
quantitative nature have scarcely been satisfactory. 
Indeed the facts of mountain geology without 
which no theory of any value could be formulated 
have become known of late years. 
After having devoted many years to the study 
of the dynamics of Mountain formation my views 
were set forth fully and scientifically in a work 
published in the latter part of 1886 * but it was 
thought that a general view of the leading features 
of my theory might prove of general interest, as 
well as forming an introduction to the larger work. 
Doubtless the primitive idea of the origin, not 
only of mountains but of valleys, is that still held 
by people who have not thought much on such sub- 
jects, that they are due to “convulsions of nature”, 
and earthquakes and volcanoes are pointed to as 
remnants of foices which acted with greater 
intensity in former ages. It is, therefore, in- 
teresting to find, in the travels of Sir John Man- 
devillo, the following rather different attempt to 
account for the origin of hills and valleys. “And 
thus have mountains and hills been, and valleys, 
which arose only from Noah’s flood, that washed 
the soft and tender ground, and fell down into 
valleys, and the hard earth and rock remain moun- 
tains where the soft and tender earth was worn 
away by the water and fell and become valleys.” 
W e have only td substitute “subserial denuda- 
tion” for Noah’s flood and we have to a large 
extent the modern notion of the origin of these 
surface features as first systematically developed 
by Hutton. 
* “ Origin of Mountain Ranges, ‘Considered Ex- 
perimewtally, Structurally, Dynamically , and in 
Relation to their Geological History.” 
Avicenna, an Arabian physician of the tenth 
century, writing on the cause of mountains, says 
“some are formed by e- setitiai, others by accidental 
causes.” A violent earthquake, by which land is 
elevated and becomes a mountain is an illustration 
of the “essential.” Excavation by water, by which 
cavities are produced and adjoining lands made 
to stand out and form eminences, is an illustration 
of the “accidental.” Confined air seeking vent, by 
which plains have been upheaved into hills, is one of 
tne geological ideas Ovid credits Pythagoras with. 
Probably most people’s elementary ideas now go 
very little further than the foregoing. I confess 
that I studied geology myself for many years with- 
out having anything but the haziest notions on the 
subject. That grand work, Lye Its Principles , to 
which geology and geologists are so much indebted, 
is unsatisfactory on the subject of the origin of 
mountain ranges, inasmuch as it is more of the 
destructive than constructive order. Lyell plainly 
sees and shows how the theory of Elie de Beau- 
mont, the only systematic theory then in existence, 
was in conflict with geological facts; but in my 
opinion Lyell fails, or, rather, does not try, to for- 
mulate any theory which may take its place. 
It appears that the idea underlying de Beau- 
mont’s theory had occurred long before to Sir Isaac 
Newton. He suggested that the cooling of the 
interior of the earth would produce compression in 
the outer crust through gravitation, as the crust 
in following the shrinking centre would be com- 
pelled to adapt inself to a less extensive area; 
hence ridges or mountains would be thrown up. 
This in the crude form is the idea underlying what 
is called the “contraction theory” of mountain for- 
mation, which has hitherto occupied perhaps the 
first place as an explanation of the origin of moun- 
tains. It is true that many geologists have been 
inclined to place expansion by heat as a cause 
more in conformity with geological fact, and it was 
long since pointed out by Babbage, Scrope and 
Herschel that the laying down of sediment would 
of itself cause a rise of temperature in the crust, 
in the same way that a top coat or blanket does in 
the human body. 
The theory was, however, never by them suffi- 
ciently developed to take the place of the earlier 
“contraction theory,” which has held its own as 
apparently invoking the only known cause suffi- 
