An historical survey of the Astronomy of the Ancients. By the Rt. Hon.
Sir G. C. Lewis.[282] 8vo. 1862.
There are few men of our day whom I admire more than the late Sir G. Lewis:
he was honest, earnest, sagacious, learned, and industrious. He probably
sacrificed his life to his conjunction of literature and politics: and he
stood high as a minister of state in addition to his character as a man of
letters. The work above named is of great value, and will be read for its
intrinsic merit, consulted for its crowd of valuable references, quoted for
its aid to one side of many a discussion, and opposed for its force against
the other. Its author was also a wit and a satirist. I know of three
classical satires of our day which are inimitable imitations: Mr.
Malden's[283] _Pragmatized Legends_, Mr. Mansel's[284] _Phrontisterion_,
and Sir G. Cornewall Lewis's _Inscriptio Antiqua_. In this last,
HEYDIDDLEDIDDLETHECATANDTHEFIDDLE etc. is treated as an Oscan inscription,
and rendered into Latin by approved methods. As few readers have seen it, I
give the result:
"Hejus dedit libenter, dedit libenter. Deus propitius [est], deus
[donatori] libenter favet. Deus in viarum {163} junctura ovorum dape
[colitur], deus mundi. Deus in litatione voluit, benigno animo, haedum,
taurum intra fines [loci sacri] portandos. Deus, bis lustratus, beat
fossam sacrae libationis."[285]
How then comes the history of astronomy among the paradoxes? Simply because
the author, so admirably when writing about what he knew, did not know what
he did not know, and blundered like a circle-squarer. And why should the
faults of so good a writer be recorded in such a list as the present? For
three reasons: First, and foremost, because if the exposure be not made by
some one, the errors will gradually ooze out, and the work will get the
character of inaccurate. Nothing hurts a book of which few can fathom the
depths so much as a plain blunder or two on the surface. Secondly, because
the reviews either passed over these errors or treated them too gently,
rather implying their existence than exposing them. Thirdly, because they
strongly illustrate the melancholy truth, that no one knows enough to write
about what he does not know. The distinctness of the errors is a merit; it
proceeds from the clear-headedness of the author. The suppression in the
journals may be due partly to admiration of the talent and energy which
lived two difficult lives at once, partly to respect for high position in
public affairs, partly to some of the critics being themselves men of
learning only, unable to detect the errors. But we know that action and
reaction are equal and contrary. If our generation take no notice of
defects, and allow them to go down undetected among merits, the next
generation will discover them, will perhaps believe us incapable of
detecting them, at least will pronounce our judgment good for nothing, and
will form an {164} opinion in which the merits will be underrated: so it
has been, is, and will be. The best thing that can be done for the memory
of the author is to remove the unsound part that the remainder may thrive.
The errors do not affect the work; they occur in passages which might very
well have been omitted: and I consider that, in making them conspicuous, I
am but cutting away a deleterious fungus from a noble tree.
(P. 154). The periodic times of the five planets were stated by
Eudoxus,[286] as we learn from Simplicius;[287] the following is his
statement, to which the true times are subjoined, for the sake of
comparison:
STATEMENT OF EUDOXUS TRUE TIME
Mercury 1 year -- 87d. 23h.
Venus 1 " -- 224d. 16h.
Mars 2 " 1y. 321d. 23h.
Jupiter 12 " 11y. 315d. 14h.
Saturn 30 " 29y. 174d. 1h.
Upon this determination two remarks may be made. First, the error with
respect to Mercury and Venus is considerable; with respect to Mercury, it
is, in round numbers, 365 instead of 88 days, more than four times too
much. Aristotle remarks that Eudoxus distinguishes Mercury and Venus from
the other three planets by giving them one sphere each, with the poles in
common. The proximity of Mercury to the sun would render its course
difficult to observe and to measure, but the cause of the large error with
respect to Venus (130 days) is not apparent.
{165}
Sir G. Lewis takes Eudoxus as making the planets move round the sun; he has
accordingly compared the _geocentric_ periods of Eudoxus with our
_heliocentric_ periods. What greater blunder can be made by a writer on
ancient astronomy than giving Eudoxus the Copernican system? If Mercury
were a black spot in the middle of the sun it would of course move round
the earth in a year, or appear to do so: let it swing a little on one side
and the other of the sun, and the average period is still a year, with
slight departures both ways. The same for Venus, with larger departures.
Say that a person not much accustomed to the distinction might for once
write down the mistake; how are we to explain its remaining in the mind in
a permanent form, and being made a ground for such speculation as that of
the difficulty of observing Mercury leading to a period four times what it
ought to be, corrected in proof and published by an industrious and
thoughtful person? Only in one way: the writer was quite out of his depth.
This one case is conclusive; be it said with all respect for the real
staple of the work and of the author. He knew well the difference of the
systems, but not the effect of the difference: he is another instance of
what I have had to illustrate by help of a very different person, that it
is difficult to reason well upon matter which is not familiar.
(P. 254). Copernicus, in fact, supposed the axis of the earth to be always
turned towards the Sun.^{(169)} [(169). See Delambre, _Hist. Astr. Mod._,
Vol. I, p. 96]. It was reserved to Kepler to propound the hypothesis of the
constant parallelism of the earth's axis to itself.
If there be one thing more prominent than another in the work of Copernicus
himself, in the popular explanations of it, and in the page of
Delambre[288] cited, it is that the _parallelism of the earth's axis_ is a
glaring part of the {166} theory of Copernicus. What Kepler[289] did was to
throw away, as unnecessary, the method by which Copernicus, _per fas et
nefas_,[290] secured it. Copernicus, thinking of the earth's orbital
revolution as those would think who were accustomed to the _solid
orbs_--and much as the stoppers of the moon's rotation do now: why do they
not strengthen themselves with Copernicus?--thought that the earth's axis
would always incline the same end towards the sun, unless measures were
taken to prevent it. He _did_ take measures: he invented a _compensating_
conical motion of the axis to preserve the parallelism; and, which is one
of the most remarkable points of his system, he obtained the precession of
the equinoxes by giving the necessary trifle more than compensation. What
stares us in the face at the beginning of the paragraph to which the author
refers?
"C'est donc pour arriver a ce parallelisme, ou pour le conserver, que
Copernic a cru devoir recourir a ce mouvement egal et oppose qui detruit
l'effet qu'il attribue si gratuitement au premier, de deranger le
parallelisme."[291]
Parallelism at any price, is the motto of Copernicus: you need not pay so
dear, is the remark of Kepler.
The opinions given by Sir G. Lewis about the effects of modern astronomy,
which he does not understand and singularly undervalues, will now be seen
to be of no authority. He fancies that--to give an instance--for the
determination of a ship's place, the invention of chronometers has been far
more important than any improvement in astronomical theory (p. 254). Not to
speak of latitude,--though the omission is not without importance,--he
ought to have known that longitude is found by the difference between what
o'clock it is at Greenwich and at the ship's place, at {167} one absolute
moment of time. Now if a chronometer were quite perfect--which no
chronometer is, be it said--and would truly tell Greenwich mean time all
over the world, it ought to have been clear that just as good a watch is
wanted for the time at _the place of observation_, before the longitude of
that place with respect to Greenwich can be found. There is no such watch,
except the starry heaven itself: and that watch can only be read by
astronomical observation, aided by the best knowledge of the heavenly
motions.
I think I have done Sir G. Lewis's very excellent book more good than all
the reviewers put together.
I will give an old instance in which literature got into confusion about
astronomy. Theophrastus,[292] who is either the culprit or his historian,
attributes to Meton,[293] the contriver of the lunar calendar of nineteen
years, which lasts to this day, that his solstices were determined for him
by a certain Phaeinus of Elis on Mount Lycabettus. Nobody else mentions
this astronomer: though it is pretty certain that Meton himself made more
than one appointment with him for the purpose of observing solstices; and
we may be sure that if either were behind his time, it was Meton. For
_Phaeinus Helius_ is the shining sun himself; and in the astronomical poet
Aratus[294] we read about the nineteen years of the shining sun:
[Greek: Enneakaideka kukla phaeinou eelioio].[295]
Some man of letters must have turned Apollo into Phaeinus of Elis; and
there he is in the histories of astronomy to {168} this day. Salmasius[296]
will have Aratus to have meant him, and proposes to read [Greek: eleioio]:
he did not observe that Phaeinus is a very common adjective of Aratus, and
that, if his conjecture were right, this Phaeinus would be the only
non-mythical man in the poems of Aratus.
[When I read Sir George Lewis's book, the points which I have criticized
struck me as not to be wondered at, but I did not remember why at the time.
A Chancellor of the Exchequer and a writer on ancient astronomy are birds
of such different trees that the second did not recall the first. In 1855 I
was one of a deputation of about twenty persons who waited on Sir G. Lewis,
as Chancellor of the Exchequer, on the subject of a decimal coinage. The
deputation was one of much force: Mr. Airy, with myself and others,
represented mathematics; William Brown,[297] whose dealings with the United
States were reckoned by yearly millions, counted duodecimally in England
and decimally in America, was the best, but not the only, representative of
commerce. There were bullionists, accountants, retailers, etc. Sir G. L.
walked into the room, took his seat, and without waiting one moment, began
to read the deputation a smart lecture on the evils of a decimal coinage;
it would require alteration of all the tables, it would impede calculation,
etc. etc. Of those arguments against it which weighed with many of better
knowledge than his, he obviously knew nothing. The members of the
deputation began to make their statements, and met with curious denials. He
interrupted me with "Surely there is no doubt that the calculations of our
books of arithmetic are easier {169} than those in the French books." He
was not aware that the _universally admitted_ superiority of decimal
_calculation_ made many of those who prefer our system for the market and
the counter cast a longing and lingering look towards decimals. My answer
and the smiles which he saw around, made him give a queer puzzled look,
which seemed to say, "I may be out of my depth here!" His manner changed,
and he listened. I saw both the slap-dash mode in which he dealt with
subjects on which he had not thought, and the temperament which admitted
suspicion when the means of knowledge came in his way. Having seen his two
phases, I wonder neither at his more than usual exhibition of shallowness
when shallow, nor at the intensity of the contrast when he had greater
depth.]