NATURE 
145 
THURSDAY, OCTOBER 26, 1916. 
“METEORITICS.” 
Meteorites: their Structure, Composition, and 
Terrestrial Relations. By Dr. O. C, Farrington. 
Pp. x+233. (Chicago: Published by the 
Author, 1915.) Price 8s. 6d. 
, | ‘HE treatise on meteorites written by the well- 
known curator of geology at the Field 
Museum of Natural History, Chicago, will meet 
a difficulty that has long faced the student who, 
while desirous of studying this subject, has hitherto 
looked round in vain for a comprehensive text- 
book. Sir L. Fletcher’s handbook and guide to 
the meteorite collection at South Kensington, 
which is now in its eleventh edition, is admirable 
so far as it goes; but its scope is naturally limited, 
since it is intended for the ordinary visitor to the 
museum. Meunier’s ‘‘ Météorites,” which formed 
part of an “Encyclopédie Chimique,” was pub- 
lished so far back as 1884, and is therefore out of 
date, and probably not now readily accessible. 
Cohen’s “Meteoritenkunde” was excellently 
planned, but was unfortunately cut short at the 
end of the third of the five parts in which it was 
intended to be by the author’s death in 1905; 
indeed, he did not live to see the third part appear. 
At the outset Dr. Farrington attempts to solve 
the problem of finding a name for the subject, and 
suggests “Meteoritics,” a word that seems to 
serve the purpose very satisfactorily, since 
“Meteoritology ” is ruled out because of the in- 
evitable confusion with that branch of science 
which is concerned with the weather. Previously 
“Astrolithology ” had been proposed by Shepard, 
and “Aerolities ” by Story-Maskelyne, but neither 
word is suitable or suggestive. 
The book. consists of two parts, though it is 
not so divided, dealing the one with the mode in 
which meteorites have reached the earth’s surface 
and their possible origin, and the other with their 
physical and chemical characters. But for the 
protection afforded by the atmosphere the fall of 
a meteorite would not be the comparatively rare 
phenomenon it is at present. Most of the erratic 
bodies which meet or overtake the earth are 
burnt up long before they reach the ground, and 
the velocity of those that do survive the passage 
through the air is so reduced by the friction that 
the rate of fall is only what would be due to gravity 
had they fallen from heights which have been 
variously estimated from 4 to 46 kilometres. 
The disruptive force generated by the heat re- 
sulting from the friction causes meteorites to 
burst into pieces which are often quite small. 
Nevertheless, some of the masses which must 
have fallen, though there is no recorded evidence 
jof the fact, have been of considerable size and 
| weight. 
xht. The largest as yet known is the 
Ahnighito—one of those located at Cape York, 
| West Greenland, by Admiral (then Lieut.) Peary 
in 1895, and now in the New York Museum; it 
weighs 364 tons. The next in size is that of 
NO. 2452, VoL. 98] 
Bacubirito, Mexico, which, on account of its in- 
accessibility and the difficulty of transport, still 
remains where it originally fell; its estimated 
weight is 27 tons. Pathetic interest attaches to 
the photograph which is reproduced as a frontis- 
piece. It represents the late Prof. H. A. Ward 
standing beside the Bacubirito meteorite. An in- 
defatigable collector of meteorites, he was ready 
to start at a moment’s notice to any part of the 
globe in search of one. He returned in safety 
from all his expeditions, only to be run over and 
killed in the street at Rochester, N.Y., where he 
had his home. y d 
Meteorites are distinguished from terrestrial 
rocks both by their structure and by their mineral 
composition. All the elements present in the 
former are known terrestrially, but some of the 
common elements, such as barium, strontium, 
lead, and bismuth, have not been detected in 
meteorites, at least not in quantity or with cer- 
‘tainty. Many of the minerals present in meteorites 
are peculiar to them, and have not been found 
terrestrially—for instance, oldhamite (calcium 
sulphide), schreibersite (iron-nickel-cobalt phos- 
phide), lawrencite (iron-nickel chloride). Their 
presence is very significant, since they could not 
have been produced had solidification taken place 
in the presence of free oxygen. It is the last- 
named mineral that is largely responsible for 
the sweating and rusting which occur in certain 
irons. The metallic portion of a meteorite con- 
sists largely of an iron-nickel alloy, and is 
arranged in a definite manner, as is shown by the 
markings developed on etching a polished section. 
Dr. Farrington himself has established that the 
nature of the arrangement depends on the ratio 
of the iron to the nickel in the alloy; irons with 
about 6 per cent. of nickel have one type, which 
is characterised by the fine Neumann lines, those 
with from 7 to 15 per cent. have a second type, 
showing the broad Widmanstatten bands, and 
those still richer in nickel have a granular struc- 
ture. Meteoritic stones are not unlike terrestrial 
rocks as regards their mineral constitution, but 
differ from them in their peculiar chondritic or 
granular structure. 
One of the problems in the subject that call 
for solution is a satisfactory classification of 
meteorites. That at present in use, which is de- 
scribed in detail by Dr. Farrington, was devised 
by Gustav Rose, and amplified or modified by 
Tschermak and Brezina. It is cumbersome, con- 
sisting as it does of no fewer than seventy-six 
groups, and has no real scientific basis. The 
author refers the reader to a scheme on the lines 
of the American quantitative classification of rocks 
which he has himself put forward. This classifi- 
cation has, however, been by no means generally 
accepted in the case’ of rocks by petrologists. A 
promising scheme, which emphasises the relation- 
ship subsisting between meteorites, however 
apparently different their characters may be, was 
recently communicated to the Mineralogical Society 
by Dr. Prior. It consists of six groups, of which 
five may be considered as derived from the first 
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