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the sun and planets was through a belt in the heavens； of a few
degrees in width； which they called the Zodiac。 They did not know；
indeed； the difference between real and apparent motion； nor the
distance of the sun and stars； nor their relative size and weight；
nor the laws of motion； nor the principles of gravitation； nor the
nature of the Milky Way； nor the existence of nebulae； nor any of
the wonders which the telescope reveals； but in the severity of
their mathematical calculations they were quite equal to modern
astronomers。
If Copernicus revolutionized astronomy by proving the sun to be the
centre of motion to our planetary system； Galileo gave it an
immense impulse by his discoveries with the telescope。 These did
not require such marvellous mathematical powers as made Kepler and
Newton immortal；the equals of Ptolemy and Hipparchus in
mathematical demonstrationbut only accuracy and perseverance in
observations。 Doubtless he was a great mathematician； but his fame
rests on his observations and the deductions he made from them。
These were more easily comprehended； and had an objective value
which made him popular： and for these discoveries he was indebted
in a great measure to the labors of others；it was mechanical
invention applied to the advancement of science。 The utilization
of science was reserved to our times； and it is this utilization
which makes science such a handmaid to the enrichment of its
votaries； and holds it up to worship in our laboratories and
schools of technology and mines； not merely for itself； but also
for the substantial fruit it yields。
It was when Galileo was writing treatises on the Structure of the
Universe； on Local Motion； on Sound； on Continuous Quantity； on
Light； on Colors； on the Tides； on Dialing；subjects that also
interested Lord Bacon at the same period；and when he was giving
lectures on these subjects with immense eclat； frequently to one
thousand persons （scarcely less than what Abelard enjoyed when he
made fun of the more conservative schoolmen with whom he was
brought in contact）； that he heard； while on a visit to Venice；
that a Dutch spectacle…maker had invented an instrument which was
said to represent distant objects nearer than they usually
appeared。 This was in 1609； when he； at the age of fifty…five； was
the idol of scientific men； and was in the enjoyment of an ample
revenue； giving only sixty half…hours in the year to lectures； and
allowed time to prosecute his studies in that 〃sweet solitariness〃
which all true scholars prize； and without which few great
attainments are made。 The rumor of the invention excited in his
mind the intensest interest。 He sought for the explanation of the
fact in the doctrine of refraction。 He meditated day and night。
At last he himself constructed an instrument；a leaden organ pipe
with two spectacle glasses； both plain on one side； while one of
them had its opposite side convex； and the other its second side
concave。
This crude little instrument； which magnified but three times； he
carries in triumph back to Venice。 It is regarded as a scientific
toy； yet everybody wishes to see an instrument by which the human
eye indefinitely multiplies its power。 The Doge is delighted； and
the Senate is anxious to secure so great a curiosity。 He makes a
present of it to the Senate； after he has spent a month in showing
it round to the principal people of that wealthy city； and he is
rewarded for his ingenuity with an increase of his salary； at
Padua； to one thousand florins； and is made professor for life。
He now only thinks of making discoveries in the heavens； but his
instrument is too small。 He makes another and larger telescope；
which magnifies eight times； and then another which magnifies
thirty times； and points it to the moon。 And how indescribable his
satisfaction； for he sees what no mortal had ever before seen；
ranges of mountains； deep hollows； and various inequalities！ These
discoveries； it would seem； are not favorably received by the
Aristotelians； however； he continues his labors； and points his
telescope to the planets and fixed stars；but the magnitude of the
latter remain the same； while the planets appear with disks like
the moon。 Then he directs his observations to the Pleiades； and
counts forty stars in the cluster； when only six were visible to
the naked eye； in the Milky Way he descries crowds of minute stars。
Having now reached the limit of discovery with his present
instrument； he makes another of still greater power； and points it
to the planet Jupiter。 On the 7th of January； 1610； he observes
three little stars near the body of the planet； all in a straight
line and parallel to the ecliptic； two on the east and one on the
west of Jupiter。 On the next observation he finds that they have
changed places； and are all on the west of Jupiter； and the next
time he observes them they have changed again。 He also discovers
that there are four of these little stars revolving round the
planet。 What is the explanation of this singular phenomenon？ They
cannot be fixed stars； or planets； they must then be moons。
Jupiter is attended with satellites like the earth； but has four
instead of one！ The importance of this last discovery was of
supreme value； for it confirmed the heliocentric theory。 Old
Kepler is filled with agitations of joy； all the friends of Galileo
extol his genius； his fame spreads far and near； he is regarded as
the ablest scientific man in Europe。
His enemies are now dismayed and perplexed。 The principal
professor of philosophy at Padua would not even look through the
wonderful instrument。 Sissi of Florence ridicules the discovery。
〃As；〃 said he； 〃there are only seven apertures of the head；two
eyes； two ears； two nostrils； and one mouth；and as there are only
seven days in the week and seven metals； how can there be seven
planets？〃
But science； discarded by the schools； fortunately finds a refuge
among princes。 Cosimo de' Medici prefers the testimony of his
senses to the voice of authority。 He observes the new satellites
with Galileo at Pisa； makes him a present of one thousand florins；
and gives him a mere nominal office；that of lecturing
occasionally to princes； on a salary of one thousand florins for
life。 He is now the chosen companion of the great； and the
admiration of Italy。 He has rendered an immense service to
astronomy。 〃His discovery of the satellites of Jupiter；〃 says
Herschel； 〃gave the holding turn to the opinion of mankind
respecting the Copernican system； and pointed out a connection
between speculative astronomy and practical utility。〃
But this did not complete the catalogue of his discoveries。 In
1610 he perceived that Saturn appeared to be triple； and excited
the curiosity of astronomers by the publication of his first
〃Enigma；〃 Altissimam planetam tergeminam observavi。 He could not
then perceive the rings； the planet seemed thr