It was not without being sensible how very unequal I am to the
undertaking, that I first consented to comply with the request of
several gentlemen for whom I have the highest esteem, and to solicit
your attention on a subject which an able hand might indeed render both
entertaining and instructive; I mean Astronomy. But the earnest desire I
have to contribute something towards the improvement of Science in
general, and particularly of Astronomy, in this my native country,
joined with the fullest confidence that I shall be favoured with your
most candid indulgence, however far I may fall short of doing justice to
the noble subject, enables me chearfully to take my turn as a member of
the society, on this annual occasion.
The order I shall observe in the following discourse, is this: In the
first place I shall give a very short account of the rise and progress
of astronomy, then take notice of some of the most important discoveries
that have been made in this science, and conclude with pointing out a
few of its defects at the present time.
As, on this occasion, it is not necessary to treat my subject in a
strictly scientific way, I shall hazard some conjectures of my own;
which, if they have but novelty to recommend them, may perhaps be more
acceptable than retailing the conjectures of others.
The first rise of astronomy, like the beginnings of other sciences, is
lost in the obscurity of ancient times. Some have attributed its origin
to that strong propensity mankind have discovered, in all ages, for
prying into futurity; supposing that astronomy was cultivated only as
subservient to judicial astrology. Others with more reason suppose
astrology to have been the spurious offspring of astronomy; a
supposition that does but add one more to the many instances of human
depravity, which can convert the best things to the worst purposes.
The honour of first cultivating astronomy has been ascribed to the
Chaldeans, the Egyptians, the Arabians, and likewise to the Chinese;[A1]
amongst whom, it is pretended, astronomical observations are to be found
of almost as early a date as the flood. But little credit is given to
these reports of the Jesuits, who it is thought were imposed on by the
natives; or else perhaps from motives of vanity, they have departed a
little from truth, in their accounts of a country and people among whom
they were the chief European travellers.
-----
Footnote A1:
The reader will find a very learned and interesting dissertation on
the astronomy of these and other nations of antiquity, in Lalande’s
_Astronomie_, liv. ii. W. B.
-----
Not to mention the prodigious number of years in which it is said the
Chaldeans observed the heavens, I pass on to what carries the appearance
of more probability;[A2] the report that when Alexander took Babylon,
astronomical observations for one thousand nine hundred years before
that time were found there, and sent from thence to Aristotle. But we
cannot suppose those observations to have been of much value; for we do
not find that any use was ever after made of them.[A3]
-----
Footnote A2:
Our orator might well pass on, without noticing more particularly the
fabulous annals of the Chaldeans. They assigned to the reigns of their
ten dynasties, 432 thousand years: and Lalande observes, that this
number, 432, augmented by two or by four noughts, frequently occurs in
antiquity. This prodigious number of years expresses, according to the
notions of the inhabitants of India, the duration of the life of a
symbolical cow: in the first age, this cow, serving as a vehicle for
innocence and virtue, advances with a firm step upon the earth,
supported by her four feet; in the second, or silver age, she becomes
somewhat enfeebled, and walks on only three feet; during the brazen,
or third age, she is reduced to the necessity of walking on two;
finally, during the iron age, she drags herself along; and, after
having lost, successively, all her legs, she recovers them in the
succeeding period, all of them being reproduced in the same order.
The Bramins thus make up their fabulous chronological account of the
age of the world; viz.
The duration of the first age, 1,728,000 years
The second 1,296,000 do.
The third 864,000 do.
The fourth will continue 432,000 do.
—————————
Making the total duration of the world 4,320,000 years.
Mr. Lalande remarks, that these four ages have a relation to the
numbers 4, 3, 2, 1, which seem to announce some other thing than an
historical division. Therefore, to give this fabulous duration of the
world some semblance of truth. Mr. Bailly[A2a] rejects, in the first
place, the fourth age, of which, at present, (that is, when Lalande
wrote,) only 4887 years have passed: the residue of this duration
could not be considered by Bailly as any thing more than a reverie:
and as for the three first ages, he takes the years for days; in order
to shew, that, in reality, they reckoned by days, before they computed
by solar years. By these means, Bailly has reduced the pretensions of
the people of India to 12,000 years; and he identifies this
calculation for the Indians with that of the Persians, who give,
likewise, 12,000 years for the duration of the world. The accordance
thus produced in the two chronologies, seemed to Bailly to strengthen
the authenticity of the recital; and makes it appear, that these
notions prevailed alike among the Egyptians and the Chinese.
Such are the data, such the calculations, and such the reasoning of
Mr. Bailly, on this subject.
But, although Mr. Lalande has noticed the retrograde series of the
progressive numbers (1,) 2, 3, 4, in the Asiatic account of the age of
the world, a kind of mysterious constitution of the amount of the
years, in the several ages which make up the entire sum of its
duration, seems to have escaped the observation of that acute
philosopher; and probably the same circumstance passed also unnoticed
by Mr. Bailly: it may be considered as a species of chronological
_abracadabra_, engendered in the prolific brain of some eastern
philosopher: the following is the circumstance here meant. It will be
perceived, in the first place, that the arrangement of the numerical
figures, in making up the years allotted to the fourth age of the
world, is apparently artificial, and therefore, probably, altogether
arbitrary. It will then be seen, that the number of years in the third
age is double the amount of those in the fourth; that those in the
second is made up by adding together the years in the fourth and third
ages; and, that those in the first age are constituted by an addition
of the number of years in the fourth and second ages. This being the
fact, it does not seem to bear out Mr. Bailly, in his hypothesis, and
the calculations founded on it. W. B.
Footnote A2a:
Mr. Bailly was the author of a _History of Ancient and modern
Astronomy_. His _Essay on the Theory of Jupiter’s Satellites_, which
is said to be a valuable treatise, was published in the year 1766.
Both works are in the French language, and were printed in France.
Footnote A3:
Lalande observes that Mr. Bailly has gone back, in his astronomical
researches, to the first traditions of an antedeluvian people, among
whom there remained scarcely any traces of such knowledge; and that he
has presented us, in his work, with ingenious conjectures and
probabilities; or, more properly, appearances of truth,
(“vraisemblables,”) written with many charms of extensive information.
But, according to Mr. Lalande himself, all the ancient astronomy down
to the time of Chiron, which was about fourteen centuries before the
Christian era, may with probability be reduced to the examining of the
rising of some stars at different times of the year, and the phases of
the moon; since, long after that period, as this great astronomer
remarks, the Chaldeans and Egyptians yet knew nothing of either the
duration or the inequalities of the planetary movements. W. B.
-----
The Egyptians too, we are told, had observations of the stars for one
thousand five hundred years before the Christian era. What they were, is
not known; but probably the astronomy of those ages consisted in little
more than remarks on the rising and setting of the fixed stars, as they
were found to correspond with the seasons of the year;[A4] and, perhaps,
forming them into constellations. That this was done early, appears from
the book of Job, which has by some been attributed to Moses, who is said
to have been learned in the sciences of Egypt.[A5] “Canst thou bind the
sweet influences of Pleiades, or loose the bands of Orion? Canst thou
bring forth Mazzaroth in his season, or canst thou guide Arcturus with
his sons?” Perhaps too, some account might be kept of eclipses of the
sun and moon, as they happened, without pretending to predict them for
the future. These eclipses are thought by some to have been foretold by
the Jewish prophets in a supernatural way.
-----
Footnote A4:
See the preceding note.
Footnote A5:
Some of the constellations appear to have been named, even before the
time of Moses, who was born 1571 years before Christ: but, probably,
most of them received their names about the time of the Argonautic
expedition, which took place in the year 1263, B. C
Hesiod and Homer who were co-temporaries, or, at least, flourished
nearly at the same time, that is to say, about nine centuries before
the Christian era, mention several of the constellations; and, among
the rest, the Bear and the Hyades: and it is noticed by Mr. Lalande,
that La Condamine says the Indians on the river Amazons gave to the
seven stars in the Hyades, the name of the Bull’s-head, as we do; and
that Father Lasitau tells us, the Iroquois called that assemblage of
stars to which we give the name of the Bear, by the same name; and
named the polar star “the star that does not move.”
These are interesting facts. There is not the least resemblance,
whatever, in the two constellations which have been mentioned, to the
animals whose names they bear. Is it not, then, a matter of great
curiosity, as well as one which may prove important in its result, to
enquire, why two great tribes of uncivilized men, (supposed, by some,
to be aborigines,) in the northern and southern sections of the
western hemisphere, should apply the same denominations to two
assemblages of stars, by which those constellations were known to
Hesiod and Homer, if not earlier, and at least twenty-five hundred
years before? W. B.
-----
As to the Arabians, though some have supposed them the first inventors
of astronomy, encouraged to contemplate the heavens by the happy
temperature of their climate, and the serenity of their skies, which
their manner of life must likewise have contributed to render more
particularly the object of their attention; yet it is said, nothing of
certainty can now be found to induce us to think they had any knowledge
of this science amongst them before they learned it from the writings of
Ptolemy, who flourished one hundred and forty years after the birth of
Christ.
But notwithstanding the pretensions of other nations, since it was the
Greeks who improved geometry, probably from its first rudiments, into a
noble and most useful science; and since we cannot conceive that
astronomy should make any considerable progress without geometry, it is
to them we appear indebted for the foundations of a science, that (to
speak without a metaphor) has in latter ages reached the astonishingly
distant heavens.
Amongst the Greeks, Hipparchus[A6] deserves particular notice; by an
improvement of whose labours Ptolemy formed that system of astronomy
which appears to have been the only one studied for ages after, and
particularly (as was said before) by the Arabians; who made some
improvements of their own, and, if not the inventors, were at least the
preservers of astronomy. For with them it took refuge, during those ages
of ignorance which involved Europe, after an inundation of northern
people had swallowed up the Roman empire; where the universally
prevailing corruption of manners, and false taste, were become as
unfavourable to the cause of science, as the ravages of the Barbarians
themselves.
-----
Footnote A6:
Hipparchus (of Nicæa, in Bithynia,) was a very celebrated
mathematician and astronomer of antiquity. Mr. Lalande styles him the
most laborious and most intelligent astronomer of antiquity, of whom
we have any record; and asserts, that the true astronomy which has
come down to us, originated with him. He divided the heavens into
forty-eight (some say forty-nine) constellations, and assigned names
to the stars. He is also said to have determined latitude and
longitude and to have computed the latter from the Canaries; and he is
supposed to be the first who, after Thales, calculated eclipses with
some degree of accuracy: but he makes no mention of comets. Hipparchus
died one hundred and twenty five years before the Christian era. W. B.
-----
From this time, we meet with little account of astronomical learning in
Europe[A7] until Regiomontanus,[A8] and some others, revived it in the
fifteenth century; and soon afterwards appeared the celebrated
Copernicus,[A9] whose vast genius, assisted by such lights as the
remains of antiquity afforded him, explained the true system of the
universe, as at present understood. To the objection of the
Aristotelians, that the sun could not be the centre of the world,
because all bodies tended to the earth, Copernicus replied, that
probably there was nothing peculiar to the earth in this respect; that
the parts of the sun, moon and stars, likewise tended to each other, and
that their spherical figure was preserved amidst their various motions,
by this power; an answer that will at this day be allowed to contain
sound philosophy. And when it was further objected to him, that,
according to his system, Venus and Mercury ought to appear horned like
the moon, in particular situations; he answered as if inspired by the
spirit of prophecy, and long before the invention of telescopes, by
which alone his prediction could be verified, “That so they would one
day be found to appear.”
-----
Footnote A7:
Friar Bacon is said to have been almost the only astronomer of his
age; he informs us that there were then but four persons in Europe who
had made any considerable proficiency in the mathematics.
Footnote A8:
Regiomontanus was born in the year 1436, at Kœnigsberg, a town of
Franconia, subject to the house of Saxe-Weimar. His real name was John
Müller: but he assumed the name of Regiomontanus from that of the
place of his nativity, which signifies _Regius Mons_.
This astronomer, who was greatly celebrated in his time, was the
first, according to Lalande, who calculated good Almanacks; which he
had composed for thirty successive years; viz. from 1476 to 1506. In
these (which were all published at Nuremberg in 1474, two years before
his death,) he announced the daily longitudes of the planets, their
latitudes, their aspects, and foretold all the eclipses of the sun and
moon; and these ephemerides were received with uncommon interest by
all nations. After noticing these, Lalande mentions the ephemerides
which are published annually at Bologna, Vienna, Berlin, and Milan;
but he pronounces the _Nautical Almanack_, of London, to be the most
perfect ephemeris that was ever published. Regiomontanus compiled
several other works, which greatly promoted his reputation, He died in
1476, at the age of forty years. W. B.
Footnote A9:
See some interesting particulars respecting this great man in Lord
Buchan’s account of the Tomb of Copernicus, and in the note thereto,
inserted in the Appendix. W. B.
-----
Next follows the noble Tycho,[A10] who with great labour and
perseverance, brought the art of observing the heavens to a degree of
accuracy unknown to the ancients; though in theory he mangled the
beautiful system of Copernicus. The whimsical Kepler, too, (whose
fondness for analogies frequently led him astray, yet sometimes happily
conducted him to important truths) did notable services to astronomy:
and from his time down to the present, so many great men have appeared
amongst the several nations of Europe, rivalling each other in the
improvement of astronomy, that I should trespass on your patience were I
to enumerate them. I shall therefore proceed to what I proposed in the
second place, and take notice of some of the most important discoveries
in this science.
-----
Footnote A10:
Tycho-Brahé, as Lalande remarks, was the first who, by the accuracy
and the number of his observations, prepared the way for the renewal
of astronomy. The theories, the tables, and the discoveries of Kepler,
are founded on his observations; and Lalande thinks, that their names,
after those of Hipparchus and Copernicus, ought to be transmitted with
immortal honour to posterity.
Tycho was born in the year 1546, at Knudsturp in Scania in Denmark, of
a noble family, which subsisted also in Sweden under the name of
Brahé, and to which the marshal count Lœwendahl was allied. He died in
1601, at the age of fifty-five years.
Frederick II, king of Denmark, gave to Tycho the little island of
Huen, called in Latin _Venusin_, towards the Sound, and about ten
leagues, northward, from Copenhagen: where that prince erected for him
a castle, named Uraniberg, and an observatory attached to it,
completely furnished with the best instruments. Yet only fifty-one
years after the death of Tycho, Mr. Huet, whose curiosity led him to
visit a place so celebrated could find no vestige of the observatory.
One solitary old man, who yet retained some recollection of it, told
him that the tempestuous winds to which they were subject along the
Sound, had demolished it. Even the name of Tycho was then unknown in
that savage island, as Mr. Lalande indignantly styles it: and Mr.
Picard, who was sent by the French academy, in 1671, to ascertain the
exact situation of the observatory, was obliged to have the earth dug
away, in order to discover its foundation. W. B.
-----
Astronomy, like the Christian religion, if you will allow me the
comparison, has a much greater influence on our knowledge in general,
and perhaps on our manners too, than is commonly imagined. Though but
few men are its particular votaries, yet the light it affords is
universally diffused amongst us; and it is difficult for us to divest
ourselves of its influence so far, as to frame any competent idea of
what would be our situation without it.[A11] Utterly ignorant of the
heavens, our curiosity would be confined solely to the earth, which we
should naturally suppose a vast extended plain; but whether of infinite
extent or bounded, and if bounded, in what manner, would be questions
admitting of a thousand conjectures, and none of them at all
satisfactory.
-----
Footnote A11:
“Certain it is,” says the learned and pious Dr. Samuel Clarke (in his
Discourse on the _Evidences of Nat. and Rev. Religion_,) “and this is
a great deal to say, that the generality, even of the meanest and most
vulgar and ignorant people,” (among Christians,) “have truer and
worthier notions of God, more just and right apprehensions concerning
his attributes and perfections, deeper sense of the difference of good
and evil, a greater regard to moral obligations and to the plain and
more necessary duties of life, and a more firm and universal
expectation of a future state of rewards and punishments, than, in any
heathen country, any considerable number of men were found to have
had.”
In like manner, Archdeacon Paley (in his _View of the Evidences of
Christianity_) observes:—“Christianity, in every country in which it
is professed, has obtained a sensible, although not a complete
influence, upon the public judgment of morals. And this is very
important. For without the occasional correction which public opinion
receives, by referring to some fixed standard of morality, no man can
foretell into what extravagances it might wander.” “From the first
general notification of Christianity to the present day,” says the
same ingenious writer, “there have been in every age many millions,
whose names were never heard of, made better by it, not only in their
conduct, but in their dispositions; and happier, not so much in their
external circumstances, as in that which is _inter præcordia_, in that
which alone deserves the name of happiness, the tranquillity and
consolation of their thoughts. It has been since its commencement, the
author of happiness and virtue to millions and millions of the human
race.” He then asks: “Who is there, that would not wish his son to be
a Christian?” W. B.
-----
The first discovery then, which paved the way for others more curious,
seems to have been the circular figure of the earth, inferred from
observing the meridian altitudes of the sun and stars to be different in
distant places. This conclusion would probably not be immediately drawn,
but the appearance accounted for, by the rectilinear motion of the
traveller; and then a change in the apparent situations of the heavenly
bodies would only argue their nearness to the earth: and thus would the
observation contribute to establish error, instead of promoting truth,
which has been the misfortune of many an experiment. It would require
some skill in geometry, as well as practice in observing angles, to
demonstrate the spherical figure of the earth from such
observations.[A12]
-----
Footnote A12:
Some of the commentators inform us, that Mahomet taught that the earth
is supported by the tip of the horn of a prodigious ox, who stands on
a huge white stone; and that it is the little and almost unavoidable
motions of this ox which produce earthquakes.
-----
But this difficulty being surmounted, and the true figure of the earth
discovered, a free space would now be granted for the sun, moon, and
stars to perform their diurnal motions on all sides of it; unless
perhaps at its extremities to the north and south; where something would
be thought necessary to serve as an axis for the heavens to revolve on.
This Mr. Crantz in his very entertaining history of Greenland informs
us, is agreeable to the philosophy of that country, with this difference
perhaps, that the high latitude of the Greenlander makes him conclude
one pole only, necessary: He therefore supposes a vast mountain situate
in the utmost extremity of Greenland, whose pointed apex supports the
canopy of heaven, and whereon it revolves with but little friction.
A free space around the earth being granted, our infant astronomer would
be at liberty to consider the diurnal motions of the stars as performed
in intire circles, having one common axis of rotation. And by
considering their daily anticipation in rising and setting, together
with the sun’s annual rising and falling in its noon day height,
swiftest about the middle space, and stationary for some time when
highest and lowest, he would be led to explain the whole by attributing
a slow motion to the sun, contrary to the diurnal motion, along a great
circle dividing the heavens into two equal parts, but obliquely situated
with respect to the diurnal motion. By a like attention to the moon’s
progress the Zodiac would be formed, and divided into its several
constellations or other convenient divisions.
The next step that astronomy advanced, I conceive, must have been in the
discovery attributed to Pythagoras;[A13] who it is said first found out
that Hesperus and Phosphorus, or the Evening and Morning Star, were the
same. The superior brightness of this planet, and the swiftness of its
motion, probably first attracted the notice of the inquisitive: and one
wandering star being discovered, more would naturally be looked for. The
splendor of Jupiter, the very changeable appearance of Mars, and the
glittering of Mercury by day light, would distinguish them. And lastly,
Saturn would be discovered by a close attention to the heavens. But how
often would the curious eye be directed in vain, to the regions of the
north and south, before there was reason to conclude that the orbits of
all the planets lay nearly in the same plane; and that they had but
narrow limits assigned them in the visible heavens.
-----
Footnote A13:
Pythagoras, who was one of the most celebrated among the Greek
philosophers, in the knowledge and study of the heavens, was born
about 540 years before the Christian era. It is believed that he was
the first who made mention of the obliquity of the ecliptic, and of
the angle which this circle makes with the equator; although Pliny
attributes this discovery to Anaximander, whose birth was seventy
years earlier. Among the remarkable things which Pythagoras taught his
disciples, was the doctrine that fire, or heat, occupied the centre of
the world; it is supposed he meant to say, that the sun is placed in
the centre of the planetery system, and that the earth revolves around
him, like the other planets. He also maintained each star to be a
world; and that these worlds were distributed in an ethereal space of
infinite extent. W. B.
-----
From a careful attendance to those newly discovered celestial
travellers, and their various motions, direct and retrograde, the great
discovery arose, that the sun is the centre of their motions; and that
by attributing a similar motion to the earth, and supposing the sun to
be at rest, all the phænomena will be solved. Hence a hint was taken
that opened a new and surprizing scene. The earth might be similar to
them in other respects. The planets too might be habitable worlds. One
cannot help greatly admiring the sagacity of minds, that first formed
conclusions so very far from being obvious; as well as the indefatigable
industry of astronomers, who originally framed rules for predicting
eclipses of sun and moon, which is said to have been done as early as
the time of Thales;[A14] and must have proved of singular service to
emancipate mankind from a thousand superstitious fears and notions,
which juggling impostors (the growth of all ages and countries) would
not fail to turn to their own advantage.
For two or three centuries before and after the beginning of the
Christian era, astronomy appears to have been held in considerable
repute; yet very few discoveries of any consequence were made, during
that period and many ages following.
-----
Footnote A14:
Thales, who died about five centuries and an half before the Christian
era, in the ninety-sixth year of his age,[A14a] first taught the
Greeks the cause of eclipses, He knew the spherical form of the earth;
he distinguished the zones of the earth by the mean of the tropicks
and the polar circles; and he treated of an oblique circle or zodiac,
of a meridian which intersects all these circles in extending north
and south, and of the magnitude of the apparent diameter of the sun.
Herodotus, Cicero, and Pliny, assert, as is noticed by Mr. Lalande,
that Thales had predicted, to the Ionians a total eclipse of the sun,
which took place during the war between the Lydians and the Medes, But
the manner in which Herodotus (who lived about one century, only,
after the time of Thales) speaks of this prediction, is so vague, that
one finds some difficulty in believing that it was fact, If it were
true, says Lalande, that Thales had actually foretold an eclipse of
the sun, it could be no otherwise, than by means of the general period
of eighteen years, of which he would have acquired a knowledge from
the Egyptians or the Chaldeans: for the period had not yet arrived,
when eclipses could be prognosticated by an exact calculation of the
motion of the moon. W. B.
Footnote A14a:
But, according to Dufresnoy, he was born in the first year of the 35th
Olympiad, and died the first year of the 52d, those periods
corresponding, respectively, with the years 640 and 572, B. C.: and if
so, he lived only sixty-eight years.
-----
The ancients were not wanting in their endeavours to find out the true
dimensions of the planetary system. They invented several very ingenious
methods for the purpose; but none of them were at all equal, in point of
accuracy, to the difficulty of the problem. They were therefore obliged
to rest satisfied with supposing the heavenly bodies much nearer to the
earth than in fact they are, and consequently much less in proportion to
it. Add to this, that having found the earth honoured with an attendant,
while they could discover none belonging to any of the other planets,
_they_ supposed it of far greater importance in the Solar System than it
appears to _us_ to be: And the more praise is due to those few, who
nevertheless conceived rightly of its relation to the whole.
Tycho took incredible pains to discover the parallax of Mars in
opposition; the very best thing he could have attempted in order to
determine the distances and magnitudes of the sun and planets. But
telescopes and micrometers were not yet invented! so that not being able
to conclude any thing satisfactory from his own observations, he left
the sun’s parallax as he found it settled by Ptolemy, about twenty times
too great. And even after he had reduced to rule the refraction of the
atmosphere, and applied it to astronomical observations, rather than
shock his imagination by increasing the sun’s distance, already too
great for _his_ hypothesis, he chose to attribute a greater refraction
to the sun’s light, than that of the stars, altogether contrary to
reason; that so an excess of parallax might be balanced by an excess of
refraction. Thus when we willingly give room to one error, we run the
risk of having a whole troop of its relations quartered upon us. But
Kepler afterwards, on looking over Tycho’s observations, found that he
might safely reduce the sun’s parallax to one minute; which was no
inconsiderable approach to the truth. Alhazen,[A15] an Arabian, had some
time before, discovered the refraction of light in passing through air;
of which the ancients seem to have been entirely ignorant. They were
indeed very sensible of the errors it occasioned in their celestial
measures; but they, with great modesty, attributed them to the
imperfections of their instruments or observations.
-----
Footnote A15:
Alhazen was one of the greatest of the Arabian astronomers. He went,
about the year 1100, to Spain, where many of his nation had
established themselves in the eighth century, and carried thither
their knowledge of astronomy; yet, from the year 800 down to about
1300, science remained shrowded with the darkest ignorance, throughout
Europe.
Mr. Lalande observes, that the theory of Refractions is an important
one, in astronomy; although it was considered of little consequence
until the time of Alhazen. W. B.
-----
I must not omit, in honour of Tycho, to observe that he first proved, by
accurate observations, that the comets are not meteors floating in our
atmosphere, as Aristotle,[A16] that tyrant in Philosophy, had determined
them to be, but prodigious bodies at a vast distance from us in the
planetary regions; a discovery the lateness of which we must regret, for
if it had been made by the ancients, that part of Astronomy (and perhaps
every other, in consequence of the superior attention paid to it), would
have been in far greater perfection than it is at this day.
-----
Footnote A16:
Aristotle, as though he had been of the race of the Ottomans, thought
he could not reign except he first killed all his brethren. Insomuch
as he never nameth or mentioneth an ancient author or opinion, but to
confute or reprove. _Bacon. Advancement._
-----
I had almost forgot to take notice of one important discovery made in
the early times of Astronomy, the precession of the equinoxes. An
ancient astronomer, called Timocharis, observed an appulse of the Moon
to the Virgin’s Spike, about 280 years before the birth of Christ. He
thence took occasion to determine the place of this star, as accurately
as possible; probably with a view of perfecting the lunar theory. About
four hundred years afterwards, Ptolemy, comparing the place of the same
star, as he then found it, with its situation determined by
Timocharis,[A17] concluded the precession to be at the rate of one
degree in an hundred years; but later astronomers have found it swifter.
-----
Footnote A17:
Timocharis of Alexandria endeavoured, with Aristillus, a philosopher
of the same school, to determine the places of the different stars in
the heavens, and to trace the course of the planets. Dr. Lempriere
places him 294 years before Christ; and the Abbé Barthelemy has
inserted his name in the list of illustrious men, who flourished in
the fourth century before the Christian era: he probably lived some
time after the commencement of that century. W. B.
-----
Whatever other purposes this great law may answer, it will produce an
amazing change in the appearance of the heavens; and so contribute to
that endless variety which obtains throughout the works of Nature. The
seven stars that now adorn our winter skies, will take their turn to
shine in summer. Sirius, that now shines with unrivalled lustre, amongst
the gems of heaven, will sink below our horizon, and rise no more for
very many ages! Orion too, will disappear, and no longer afford our
posterity a glimpse of glories beyond the skies! glittering Capella,
that now passes to the north of our zenith, will nearly describe the
equator:[A18] And Lyra, one of the brightest in the heavens, will become
our Polar Star: Whilst the present Pole Star, on account of its humble
appearance, shall pass unheeded; and all its long continued faithful
services shall be forgotten! All these changes, and many others, will
certainly follow from the precession of the equinoxes; the cause of
which motion was so happily discovered and demonstrated by the immortal
Newton: A portion of whose honors was nevertheless intercepted by the
prior sagacity of Kepler, to whom I return.
-----
Footnote A18:
By its peculiar situation it will continue to do so for a long time.
-----
Kepler’s love of harmony encouraged him to continue his pursuits, in
spite of the most mortifying disappointments, until he discovered that
admirable relation which subsists between the periodic times of the
primary planets, and their distances from the sun; the squares of the
former being as the cubes of the latter. This discovery was of great
importance to the perfection of Astronomy; because the periods of the
planets are more easily found by observation, and from them their
several relative distances may be determined with great accuracy by this
rule. He likewise found from observation, that the planets do not move
in circles; but in elipses, having the sun in one focus. But the causes
lay hid from him, and it was left as the glory of Sir Isaac, to
demonstrate that both these things must necessarily follow from one
simple principle, which almost every thing in this science tends to
prove does really obtain in Nature: I mean, that the planets are
retained in their orbits by forces directed to the sun; which forces
decrease as the squares of their distances encrease.
Kepler also discovered that the planets do not move equally in their
orbits, but sometimes swifter, sometimes slower; and that not
irregularly, but according to this certain rule; That in equal times,
the areas described by lines drawn from the planet to the sun’s centre,
are equal. This, Sir Isaac likewise demonstrated must follow, if the
planet be retained in its orbit by forces directed to the sun, and
varying with the distance in any manner whatsoever. These three
discoveries of Kepler, afterwards demonstrated by Newton, are the
foundation of all accuracy in astronomical calculations.[A19]
-----
Footnote A19:
According to Lalande, Kepler was as celebrated in astronomy by the
consequences he drew from the observations of Tycho Brahé, as the
latter was for the immense mass of materials which he had prepared for
him: and the Abbé Delaporte (in his _Voyageur François_) represents
him as precursor of Descartes in opticks, of Newton in physicks, and
as a law-giver (“_legislateur_”) in astronomy.
John Kepler, for this was the name of that famous mathematician, was
born at Wiel, in the duchy of Wirtemberg, in the year 1571; and the
Abbé Delaporte says, his family was illustrious. He died at Ratisbon,
in 1630. W. B.
-----
We now come to that great discovery, which lay concealed from the most
subtle and penetrating geniuses amongst mankind, until these latter
ages; which so prodigiously enlarged the fields of astronomy, and with
such rapidity handed down one curiosity after another, from the heavens
to astonished mortals, that no one capable of raising his eyes and
thoughts from the ground he trod on, could forbear turning his
attention, in some degree, to the subject that engages us this evening.
Galileo, as he himself acknowledges, was not the first inventor of the
telescope, but he was the first that knew how to make a proper use of
it.[A20] If we consider that convex and concave lenses had been in use
for some centuries, we shall think it probable that several persons
might have chanced to combine them together, so as to magnify _distant_
objects; but that the small advantage apparently resulting from such a
discovery, either on account of the badness of the glasses or the
unskilfulness of the person in whose hands they were, occasioned it to
be neglected.
-----
Footnote A20:
The true invention of the telescope cannot be carried back to an
earlier date than the beginning of the seventeenth century. Johannes
Baptista Porta, a Neapolitan, in his _Natural Magic_, which was
published in the year 1589, says, “_Si utramque (lentem concavam et
convexam) recté componere noveris, et longinqua et proxima majora et
clara videbis_:” and he is said to have made a telescope, accordingly,
about the year 1594. But Porta is represented as having made this
discovery such as it was, by accident; and, as not well understanding
the proper use of his own invention.
According to Baron Bielfeld,[A20a] however, telescopes were first
constructed a long time after, in Holland; some say, by John
Lippersheim, a spectacle-maker at Middelbourg in Zealand; others, by
James Metius, brother to the celebrated professor Adrian Metius, of
Franeker. Although the invention of this instrument, of indispensable
use in astronomy, is sometimes attributed to the great Galileo, he has
himself acknowledged, in his treatise, entitled _Nuncius Siderius_,
that he took the hint from a report of a German having invented an
instrument, by means of which, and with the assistance of certain
glasses, distant objects might be distinguished as clearly as those
that were near. This is precisely what Porta had mentioned in his
book, in 1589; and therefore, if Galileo had not referred to a German,
he might be supposed to have had in his view the Neapolitan’s
conception of a telescope, announced long before such an instrument
was properly constructed.
Whatever may have been the merit of Porta’s discovery, or the
pretensions of Lippersheim, the spectacle-maker, and Metius, Peter
Borel (in his treatise _De vero Telescopii Inventore_) is of the
opinion that Zachariah Johnson, who, like Lippersheim, was a
spectacle-maker, and in the same city, made this discovery by chance,
about the year 1500; that Lippersheim imitated him, after making
numerous experiments; and that he instructed Metius. There are others,
who have been considered as having had some sort of claim to this
important invention; among whom were a Mr. Digges, of England, and a
M. Hardy, of France, both towards the commencement of the seventeenth
century.
It is certain, however, that Galileo in Italy, (who died in 1642, aged
seventy-eight years,) and, according to Bielfeld, Simon Marius in
Germany, were the first that applied the telescope to the
contemplation of celestial objects. W. B.
Footnote A20a:
_Elem. of Univ. Erud._ b. i. ch. 49.
-----
But Galileo, by great care in perfecting his telescope, and by applying
a judicious eye, happily succeeded; and with a telescope magnifying but
thirty times, discovered the moon to be a solid globe, diversified with
prodigious mountains and vallies, like our earth; but without seas or
atmosphere. The sun’s bright disk, he found frequently shaded with
spots, and by their apparent motions proved it to be the surface of a
globe, revolving on its axis in about five and twenty days. This it
seems was a mortifying discovery to the followers of Aristotle; who held
the sun to be perfect without spot or blemish.[A21] Some of them, it is
said, insisted that it was but an illusion of the telescope and
absolutely refused to look through one, lest the testimony of their
senses should prove too powerful for their prejudices.
-----
Footnote A21:
In treating of the astronomy of the Greeks, Lalande contents himself
with barely introducing the name of Aristotle, among their
philosophers; seeming to consider him as one who had done very little
for astronomical science. This philosopher (who died in the
sixty-third year of his age, and only 322 years B. C.) among his other
doctrines, not only maintained the eternity of the world; but, that
Providence did not extend itself to sublunary beings: and as to the
immortality of the soul, it is uncertain whether he believed it or
not. Bayle calls his logic and his natural philosophy, “the weakest of
his works:” and says, further; “It will be an everlasting subject of
wonder to persons who know what philosophy is, to find that
Aristotle’s authority was so much respected in the schools, for
several ages, that, when a disputant quoted a passage from this
philosopher, he who maintained the thesis durst not say, _Transeat_;
but must either deny the passage or explain it in his own way.” W. B.
-----
Galileo likewise discovered the four attendants of Jupiter, commonly
called his satellites:[A22] Which at first did not much please that
great ornament of his age, the sagacious Kepler. For by this addition to
the number of the planets, he found their Creator had not paid that
veneration to certain mystical numbers and proportions, which he had
imagined. Let us not blush at this remarkable instance of philosophical
weakness, but admire the candour of the man who confessed it.
-----
Footnote A22:
This discovery was made on the 8th of January, 1610. It was, as Mr.
Vince observes, a very important one in its consequences; as it
furnished a ready method of finding the longitude of places, by means
of their eclipses. W. B.
-----
Galileo not only discovered these moons of Jupiter, but suggested their
use in determining the longitude of places on the earth; which has since
been so happily put in practice, that Fontenelle does not hesitate to
affirm, that they are of more use to Geography and Navigation,[A23] than
our own moon. He discovered the phases of Mars and Venus; that the
former appears sometimes round and sometimes gibbous, and that the
latter puts on the shapes of our moon: And from this discovery, he
proved to a demonstration, the truth of the Copernican System.[A24] Nor
did that wonderful ring, which surrounds Saturn’s body, without touching
it, and which we know nothing in nature similar to, escape his notice;
though his telescope did not magnify sufficiently to give him a true
idea of its figure.
-----
Footnote A23:
Although both Geography and Navigation have been wonderfully improved
by the important discoveries made by the moderns in astronomy, they
have nevertheless, derived the most essential aid from the application
of the Compass to their purposes.
The invention of this instrument, which is of indispensible utility,
is almost universally ascribed to Flavio Gioia, a native of Amalfi in
the kingdom of Naples. He is called, by some writers, Flavio de Melfi,
(by which is meant, Flavio of Amalfi, this town being the place of his
nativity;) and his invention of the Compass is placed in the year
1302. But it is affirmed by others, that Paulus Venetus brought the
Compass first into Italy from China, in the year 1260. The Chinese
Compass, however, whatever may be its antiquity, appears to have been
a very imperfect instrument, compared with the modern Mariner’s
Compass; and, more especially, with the Azimuth Compass, as improved
by Dr. Knight and Mr. Smeaton. The Chinese Compass, now used, is
represented as being nothing more than a magnetic needle kept
floating, by means of a piece of cork, on the surface of water, in a
white china ware vessel, divided at bottom into twenty-four points.
It is worthy of observation, that the French have laid claim to the
invention of the Compass, upon no better foundation than the
circumstance of a _fleur de lys_ being always placed at the north
point of the chard; although it is known, that Gioia decorated the
north end of the needle with that flower in compliment to his own
sovereign, who bore it in his arms, as being descended from the royal
house of France. “It hath been often,” says Dr. Robertson,[A23a] “the
fate of those illustrious benefactors of mankind, who have enriched
science and improved the arts by their inventions, to derive more
reputation than benefit from the happy efforts of their genius. But,”
continues this eminent historian, “the lot of Gioia has been still
more cruel; through the inattention or ignorance of contemporary
historians, he has been defrauded even of the fame to which he had
such a just title. We receive from them no information with respect to
his profession, his character, the precise time when he made this
important discovery, and the accidents and enquiries which led to it:
the knowledge of this event, though productive of greater effects than
any recorded in the annals of the human race, is transmitted to us
without any of those circumstances which can gratify the curiosity
that it naturally awakens.” W. B.
Footnote A23a:
Hist. of America, vol. i, b. i.
Footnote A24:
Galileo Galilei was a strenuous defender of the system of Copernicus;
for which he was condemned by the inquisition, in the year 1635, under
Pope Urban VIII. This extraordinary man was a native of Florence, and
born in 1564. He died in 1642, aged seventy-eight years.