# Bauhaus-Universität Weimar

### Volltext Typical laws of heredity (15)

Titel:
Typical laws of heredity
Person:
Galton, Francis
PURL:
https://digitalesammlungen.uni-weimar.de/viewer/image/lit15962/4/
```495
April 5, 1877] NA T U RE
It is indeed a strange fact that any one of us sitting
quietly at his table could, on being told the two numbers
just mentioned, draw out a curve on ruled paper, from
which thousands of vertical lines might be chalked side
by side on a wall, at the distance apart that is taken up
by each man in a rank of American soldiers, and know
that if the same number of these American soldiers taken
indiscriminately had been sorted according to their heights
and marched up to the, wall, each man .of them would find
the chalked line which he found opposite to him to be of
exactly his own height So far as 1 can judge from the
run of the figures in the table, the en-or would never
exceed a quarter of an inch, except at either extremity of
the series.
The principle of the law of deviation is very simple.
The important influences that acted upon each pellet were
the same ; namely, the position of the point whence it was
dropped, and the force of gravity. So far as these are
concerned, every pellet wo’Jtd have pursued an identical
path. But in addition to these there were a host of petty
disturbing influences, represented by the spikes among
which the pellets tumbled in all sorts of ways. The
theory of combination shows that the commonest case is
that where a pellet falls equally often to the right of a
spike as to the left of it, and therefore drops into the
compartment vertically below the point where it entered
the harrow. It also shows that the cases are very rare of
runs of luck carrying the pellet much oftener to one side
than the other, . The law of deviation is purely numeri¬
cal ; it does not regard the fact whether the objects
treated of are pellets in an apparatus like this, or shots
at a target, or games of chance, or any other of the
numerous groups of occurrences to which it is or may be
applied.1
I have now done with my description of the law. I
know it has been tedious, but it is an extremely difficult
topic to handle on an occasion like this. I trust the
application oi it will prove of more interest.
{To be continued
ON THE STRUCTURE AND ORIGIN OF
METEORITES*
THE study of meteorites is naturally divisible into
several very distinct branches of inquiry. Thus in
the first place we may regard them as shooting stars, and
observe and discuss their radiant points and their relation
to the solar system. This may be called the astronomical
aspect of the question. Then, when solid masses fall to
the ground, we may study their chemical composition as
a whole, of that of the separate mineral constituents ; and
lastly, we may study their mechanical structure, and apply
to this-investigation the same methods which have yielded
such important results in, the case of terrestrial rocks.
So much has been written on the astronomical, chemical,
and mineralogical aspect of my subject by those far more
competent than myself to deal with such questions, that I
shall confine my remarks almost entirely to the mechani¬
cal structure of meteorites and meteoric irons, and more
especially to my own observations, since they will, at all
events, have" the merit of greater originality and novelty.
Time will, however, not permit me to enter into the detail
even of this single department of my subject.
. In treating this question it appeared to me very desir¬
able to exhibit to you accurate reproductions of the natural
objects, and I have therefore had prepared photographs
of my original drawings, which we shall endeavour to
show by means of the oxyhy drogen lime-light, and I shall
modify my lecture to meet the requirements of the case,
1 Quetelet, apparently from habit rather than theory, always adopted the
binomial law of error, basing his tables on a binomial of high power. It is
absolutely necessary to ihe theory of the present paper, to get rid of binomial
limitations and to consider the law of deviation or error, in its exponential
form. . ,
2 Abstract of lecture delivered by H. C Sorby, F.R.S., &c., at tne
Museum, South Kensington, on March 10. • .
exhibiting and describing special examples, rather than
attempt to give an account of meteorites in general
Moreover, since the time at my disposal is short, and their
external characters may be studied to great advantage at
the British Museum, I shall confine my remarks as much
as possible to their minute internal structure, which can
be seen only by examining properly prepared sections
with more or less high magnifying powers.
By far the greater part of my observations were made
about a dozen years ago. Î prepared a number of sections
of meteorites, meteoric irons, and other objects which
might throw light on the subject, and my very best thanks
are due to Prof. Maskelyne for having most kindly allowed
me to thoroughly examine the very excellent series of
thin sections, which had been prepared for him. During
the last ten years my attention has been directed to very
different subjects, and I have done little more than collect
material for the further and more complete study of
meteorites. When I have fully utilised this material I
have no doubt that I shall be able to make the subject far
more complete, and may find it necessary to modify some
of my conclusions. I cannot but feel that very much more
remains to be learned, and I should not have attempted
to give an account of what I l*ave so far done, if I had
not been particularly asked to do so by Mr. Lockyer. At
the same time I trust that I shall at all events succeed in
showing that the microscopical method of study yields
such well marked and important facts, that in some cases
the examination of only a single specimen serves to decide
between rival theories. 7 •
In examining With the naked eye an entire or broken
meteorite we see that the original external outline is very
irregular, and that it is covered by a crust, usually, but
not invariably black, comparatively thin, and quite unlike
the main mass inside. This crust is usually dull, but
sometimes, as in the Stannern meteorite, bright and shin¬
ing, like a coating of black varnish. On examining with
a microscope a thin section of the meteorite, cut perpen¬
dicular to this crust, we see that it is a true black glass
rilled with small bubbles, and that the contrast between it
and the main, mass of the meteorite is as complete as
possible, and the junction between them sharply defined,
except when portions have been injected a short distance
between the crystals. We thus have a most complete
proof of the conclusion that the black crust was due to
the true igneous fusion of the surface under conditions
which had little or no influence at a greater depth
than -rivth of an inch. In the case of meteorites of dif¬
ferent chemical composition, the black crust has not re¬
tained a true glassy character, and is sometimes j^tb of
an inch in thickness, consisting of two very distinct layers,
the internal showing particles of iron which have been
neither melted nor oxidised, and the external showing that
they have been oxidised and the oxide melted up with the
surrounding stony matter. Taking everything into con¬
sideration, the microscopical structure of the crust agrees
perfectly well with the explanation usually adopted, but
rejected by some authors, that it was formed by the fusion
of the external surface, and was due to the very rapid
heating which takes place when a body moving with
planetary velocity rushes into the earth’s atmosphere—a
heating so rapid that the surface is melted before the heat
has time to penetrate beyond a very short distance into
the interior of the mass. .
When we come to examine the structure of the original
interior part of meteorites, as shown by fractured surfaces,
we may often see with the naked eye that they are
mottled in such a way as to have many of the characters
of a brecciated rock, made up of fragments subsequently
cemented together and consolidated. Mere rough frac¬
tures are, however, very misleading. A much more
accurate opinion may be formed from the examination of
a smooth flat surface. Facts thus observed led Reichen-
bach to conclude that meteorites had been formed by the
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