WAT ORE 
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THURSDAN) APRIL rr, 1907: 
MECHANISM OF THE WORLD. 
The World Machine. The First Phase, the Cosmic 
Mechanism. By Carl Snyder. Pp. xvi+488. 
(London: Longmans, Green and Co., 1907.) 
gs. net. 
N this boolx the author purposes ‘‘ to go back to the 
simplest beginnings of things—to the days when 
primitive man first learned to count, to measure, to 
time, and to weigh, and to mark out how his every 
step towards positive knowledge has been an advance 
toward mechanical conceptions of phenomena which 
must one day end in a mechanical conception of the 
whole.’’? Two-thirds of the book are therefore de- 
voted to a history of man’s ideas about the construc- 
tion of the universe, while the remaining pages give 
an account of the results of the investigations of the 
present day. Among his predecessors the author 
mentions Pliny and Humboldt. It would be unfair 
to blame him for not coming up to the high level of 
Humbol¢!, but it is unfortunate that he too often 
resembles Pliny in not having understood his sources 
properly, without resembling him in presenting his 
readers with a great mass of detail. The narrative 
is very verbose, and does not clearly show how one 
idea or group of ideas has been developed from 
previous ones. 
The author has evidently not studied the original 
works of the heroes of science whose judge he has 
constituted himself, as he is anything but a trust- 
worthy guide in the history of astronomy. Among 
the historical works consulted he mentions Schia- 
parelli’s memoir on the precursors of Copernicus, but 
he can hardly have read it carefully, since he repeats 
the old errors about Pythagoras and Philolaus having 
taught the heliocentric system. Mr. Snyder is not 
interested in those philosophers who did not know 
that the earth moves round the sun, and Plato and 
Aristotle are dealt with very severely. Though he 
acknowledges that Plato knew something of geo- 
metry, he thinks that “the puerile phantasies with 
which his pages are strewn do not give us a very 
high idea of his powers of mind.’ Aristotle “cuts 
rather a sorry figure as a thinker,’’ and the only 
philosopher of antiquity who finds favour in the 
author’s sight is Demokritus, on account of his 
atomic theory. 
That the earth is a sphere the author imagines 
was undoubtedly known to the Egyptian priests, who 
communicated this discovery to Thales; and in several 
places it is hinted that the Egyptians and Babylonians 
knew a great deal more about the construction of 
the world than the Greeks ever did in after times. 
This was the belief of Bailly (whom the author quotes 
among his authorities), but the discoveries of 
archzologists have long ago shown it to be devoid 
of the slightest foundation. Among the Greeks, the 
author (or his source) fixes on a certain Bion, said 
te have been a disciple of Demokritus, but otherwise 
NO. 1954, VOL. 75 | 
Price 
unknown, as the first to have worked out in detail 
the doctrine of the sphericity of the earth. This is 
done solely on the authority of Diogenes Laertius, 
who says that Bion was the first to assert that there 
are countries where there is day for six months and 
night for six months. That Parmenides and Pytha- 
goras had announced the spherical form of the earth 
and divided it into five zones at least fifty years 
earlier is not mentioned. 
The various measures of the size of the earth are 
next dealt. with, and it is stated that we do not know 
the exact value of a stadium. It is, however, now 
quite. certain that the stadium of Eratosthenes was 
equal to 157-5 metres, being the measure employed 
by the bematists or professional pacers, and that 
Posidonius used the same. Their results for the cir- 
cumference of the earth, 252,000 and 240,000 stadia, 
were therefore not very discordant, and the former 
was remarkably near to the truth. Ptolemy, who 
gives 180,000 stadia, employed the official or Royal 
Egyptian stadium of 210 metres, so that he, in other 
words, simply adopted the value of Posidonius. That 
Columbus thought India much nearer to Spain than 
it really is was therefore not caused by an error of 
Ptolemy in making the earth too small, but by his 
believing Asia to extend much further east than it 
does. 
If the author does scant justice to Eratosthenes in 
this matter, he certainly gives him far too much 
credit with regard to his idea of the distance of the 
sun. We are told that, according to the ‘‘ Placita 
Philosophorum,”’ Eratosthenes gave this distance as 
804 million stadia, a wonderful approximation to the 
truth. So it would have been, but unfortunately the 
correct reading of the passage in question is 4,080,000 
stadia, so that we need not trouble ourselves to find 
out how Eratosthenes came to know the distance of 
the sun so very accurately. Neither was the know- 
ledge of Posidonius on this matter very miraculous, 
for when he assumed the sun’s distance to be 
500 million stadia, it was a perfectly arbitrary 
assumption, in which he merely followed Archimedes. 
In his ‘f Arenarius,’’ Archimedes had purposely made 
the circumference of the earth equal to three million 
stadia, in order to have large numbers to operate 
with, and the circumference of the solar orbit ten 
thousand times as great. 
No attempt is made to show how Aristarchus may 
have been led to suggest that the earth moves round 
the sun, but here, as everywhere else, the author fails 
to realise the state of science of past ages, and 
thinks that it ‘‘ passes understanding ’’ that Archi- 
medes could accept the geocentric system. The 
wonderful progress of mathematical astronomy, 
culminating in the work of Ptolemy, is quite ignored, 
and the picture of Greek astronomy presented by Mr. 
Snyder is on the whole a very misleading one. Pass- 
ing to Copernicus, we find it stated that he discarded 
the system of epicycles, while the truth is that he 
had to employ them very largely, because he did not 
know the two first laws of Kepler. The “ third 
motion’? of the earth assumed by Copernicus has 
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