Page:Popular Science Monthly Volume 31.djvu/373

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359
EARTHQUAKES.

his brain is smaller than when he was a boy between seven and fourteen, the age when he thought he knew the most.

Dr. Paul Broca gave the following table of average brain-weights:

From  1 to 10 years,   985·15 grammes (34·7  oz.).
From 11 to 20 years, 1,465·27 " (51·68 oz.).
From 21 to 30 years, 1,341·53 " (47·67 oz.).
From 31 to 40 years, 1,410·36 " (49·74 oz.).
From 41 to 50 years, 1,391·41 " (49·07 oz.).
From 51 to 60 years, 1,341·19 " (47·30 oz.).
61 and upward, 1,326·21 " (46·77 oz.).

By looking over Dr. Boyd's table it will be seen that heavy brains generally belong to tall men; and so, by our table of individuals, it appears that the heaviest is that of Turgeneff, who was a man of large size, while the lighter brains accompanied men of medium or short stature. Women are generally shorter than men, and their brains relatively smaller. Quatrefages says: "We have known for several years that the stature has an influence upon the weight of the brain. It can not be without influence upon the cavity by which the latter is inclosed. Under similar circumstances in other respects, the weight of the brain varies proportionately, or almost proportionately, to the height."

If we accept the above statement that the largest healthy brains are found in the tallest persons, and add to it the phrenological rule that brain-size is a true measure of mental power, it will follow that giants have the greatest minds in the world, which is contradicted by every day's experience. Dr. Ireland, in his work on idiocy and imbecility, mentions two cretins, each six feet high; several idiot Calibans, six feet six inches; several idiots described by Lomboso, one of whom was eight and a half feet, another seven feet eight inches, with a sister the same height. Large stature may be a general indication of large brain-weight, but the latter can not be taken as a safe index of high intellectual power.

 

EARTHQUAKES.
By Professor G. H. DARWIN, F. R. S.

THE earthquake-shocks which have recently occurred in America and Greece, and the great volcanic eruption in New Zealand, have served to keep the subject vividly before us during many months past, and have perhaps created in some alarmist minds an ungrounded expectation that the earth is about to enter on a new period of Plutonic activity. It is natural, then, to ask at the present time what is an earthquake, and what are its causes. Notwithstanding the necessary incompleteness in the answers which can be given to these questions, yet a good deal more is known than appears to be the common property of newspaper writers. The object, then, of the present article is