138 
THE MEDITERRANEAN NATURALIST 
systematic theory of normal faulting before the 
one broached by me in the a Origin of Mountain 
Kanges” (Chapter viii.) Detached thoughts on the 
subject there have been, and it would not be 
difficult to prove that glimmerings of light have 
occurred to many without the illumination being 
sufficient to allow the observer to commit himself 
to anything like a complete generalisation. 
Those who are interested in the question will do 
well to read a paper by Mr. W. J. McGee, of the 
United States Geological Survey ant. in the No- 
vember number of the Geological Magazine .(1) 
It is evident that American geologists are moving 
in the direction of the explanations of the cor' uga- 
tions of the earth’s surface herein advocated. It is 
unnecessary to quarrel over the exact amount of 
novelty of view to be awarded to this or that 
investigator. If the view gains credence slowly, so 
much the more stable are they likely to become. 
Mr. McGee says — “A primary hypothesis ascrib- 
ed the corrugation of the terrestial crust to con- 
traction of the interior of the earth, accompanying 
secular cooling more rapid than that of the exterior 
shell. The common conception of the mechanism 
of this process was familiarly illustrated by likening 
the corrugated globe to a withered apple, and the 
inequalities of the terrestial surface to the 
wrinkles on the apple’s skin; and to the surprise 
of most American geologists at least, this hy- 
pothesis has been prominently advocated within a 
year or two.” 
No account of mountain formation would be 
complete without some discussion of vulcanolgy. 
To this phase of the dynamics of the earth I pro- 
pose to devote the next article. 
( To be continued.) 
(1) “ Some difficulties in Dynamical Geology” p. 
493. Geo. Mag , 1888. 
In the Philosophical Magazine for Mary 1891 
republished in the American Geologist. Nov. 1891, 
those interested will find answers to recent criti- 
cisms and, some reference to the history of these 
ideas in ic An outline of Mr. M.ellard Readds theory 
of the origin of Mountain Ranges by sedimenta- 
ry loading and cumulative recurrent expansion A 
Science Gossip. 
Messers. Dulau k Co. of Soho Square London, 
and Mr. W. P. Collins of 154 Gt. Portland St. 
London have just issued their book -catalogues, in 
which every branch of natural science is represent d. 
We have to acknowledge the receipt of one of 
the most complete and useful works of the year. 
The Annals of British Geology for 1890 is a book 
which no geologist can afford to be without, in as 
much at it contains hot only a full and accurate 
list of the papers on geological science that were 
published in Great Britain in 1890, but also a 
critical digest and succint account of those papers 
together with a number of personal items bearing 
on the progress of science during the year. The 
abstract of Dr. John Murray’s papers on the 
Maltese Islands will be of special interest to 
Maltese naturalists. The work may be obtained 
from the author Prof. J. Blake, 43 Clifton Hill, 
London, N. W. 
In a paper on the camel, Herr Lehmann states 
that neither heat nor cold, nor extreme daily or 
yearly variations, impede the distribution of the 
camel, — each race of camels being, however, best 
adapted to the conditions of its native climate. 
The dromedary of the Sahara enjoys its best health 
in the desert, though a day of tropical heat may 
be followed by a night several degrees below 
freezing-point, and daily variations of 60° occur. 
In Semipalatinsh again, where camels are found, 
the annual variation sometimes reaches nearly 150°. 
But the camel is very sensitive to moistare, and 
desert caravans run much risk in entering regions 
of tropical rain during the rainy season. 
Prof. Edwin J. Houston remarks that, during 
the general prevalence of moist warm air, a fall of 
rain might be produced by the sudden opening 
of cylinders of liquefied gases, whose expansion 
would cause the chilling of the surrounding air 
necessary to condense the moisture. The present 
state of meteorological science justifies these con- 
clusions :(1) That rain can never be made to fall 
at will by mid-air explosions on any part of the 
