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those, whose labors we are constantly reaping. We riot in a profusion of fruits, on the culture of which we have bestowed no care. The results of numerous experiments have become common property. Long-cherished theories have been exploded by the light of truth. The principles of investigation have become known and established. An apparatus for the learner and the professor, is as familiar as the tools of the mechanic. But all this was not acquired in a day, nor yet in a century. Genius wrought out inventions and made discoveries, without precedents, without tools or helpers ; and against the combined power of ignorance and self-interest, accredited them with the world.

GALILEO was one of the most distinguished among the pioneers of science. His name, and slight portions of his history, are familiar to all. This is not sufficient. His labors and their results should be well pondered and understood. He is entitled to this distinction, whether we consider the acumen, diligence and perseverance of the man ; the importance of his discoveries ; their influence on the extension of knowledge and the science of investigation; or the unfavorable period in which he lived, and the mountain difficulties with which he contended. To establish his claims to the attention of every American student, we need only notice his principal discoveries which may be seen at a glance in the table of contents. These were made at a time, when the least innovation on received principles was sure to incur, both the odium of the populace and the persecutions of the Romish bierachy. Yet this profound philosopher, confident in his principles as based or: rccitrovertible facts, braved all discouragements and dangers, and her queathed his discoveries and his fame as a precious legacy to succeeding generations.

This brief and comprehensive account of the distinguished Italian, was. prepared in England, for the Library of Useful Knowledge, and is now published separately for more general use.

CONTENTS.

IHAPTER

PAGK.
I-Introduction.

13
II.-Galileo's birth-Family-Education_Obser-

vation of the Pendulum--Pulsilogies—

Hydrostatical Balance—Lecturer at Pisa. 20
III.-Galileo at Pisa-AristotleLeonardo da Vin-

ci-Galileo becomes a Copernican-Urs-
tisius--Bruno--Experiments on falling

bodies-Galileo at Padua-Thermometer. 30
IV.-Astronomy before Copernicus—Fracastoro—

Bacon-Kepler-Galileo's treatise on the

Sphere.
V.-Galileo re-elected Professor at Padua-New

Star-Compass of Proportion-Capra-
Gilbert--Proposals to return to Pisa

-
Lost Writings-Cavalieri.

65
VI.-Invention of the Telescope-Fracastoro-

Porta-Reflecting Telescope-Roger Ba-
con--Digges-—-De Dominism Jansen-
Lipperhey-Galileo constructs Teles-
copes—Microscopes—Re-elected Profes-
sor at Padua for life.

67

CHAPTER.

PAGE.

VII.-Discovery of Jupiter's Satelites--Kepler--

Sizzi-Astrologers---Mæstlin--Horkey-
Mayer.

84
VIII.--Observations on the Moon--Nebulæ--Saturn--
Venus-Mars

104
IX.-Account of the Academy at Lincea-Del Cim-
ento-Royal Society.

114
X.-Spots on the Sun-Essay on Floating Bodies-
Scheiner-Change in Saturn.

123
XI.—Letter to Christina, Arch-Duchess of Tusca-

ny--Caccini ---Galileo re-visits Rome--
Inchaffer-Problem of Longitudes.

142
XII.-Controversy on Comets—Saggiatore-Galileo's

reception by Urban VIII–His Family. 158
XIII.-Publication of Galileo's System of the World—

His condemnation and Abjuration. 167
XIV.-Extracts from the Dialogues on the System. 196
XV.-Galileo at Arcetri --Becomes Blind-Moon's

Libration. ---Publication of the Dialogues
on Motion.

222
XVI.--State of the Science of Motion before Galileo. 232
XVII.--Galileo's Theory of Motion-Extracts from
the Dialogues.

248
XVIII.--Correspondence on Longitudes--Pendulum
Clock.

274
XIX.-Character of Galileo-Miscellaneous details
His Death-Conclusion.

291
ZAIVAT

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The knowledge which we at present possess of the phenomena of nature and of their connection, has not by any means been regularly progressive, as we might have expected, from the time when they first drew the attention of mankind. Without entering into the question touching the scientific acquirements of castern nations at a remote period, it is certain that some among the early Greeks were in possession of several truths, however acquired, connected with the economy of the universe, which were afterwards suffered to fall into neglect and oblivion. But the philosophers of the old school appear in general to have confined themselves at the best to observations; very few traces remain of their 1 ; instituted experiments, properly so called. T) tting of nature to the tor

B

The ex

ture, as Bacon calls it, has occasioned the principal part of modern philosophical discoveries. perimentalist may so order his examination of nature as to vary at pleasure the circumstances in which it is made, often to discard accidents which complicate the general appearances, and at once to bring any theory which he may form to a decisive test. The province of the mere observer is necessarily limited; the power of selection among the phenomena to be presented is in great measure denied to him, and he may consider himself fortunate if they are such as to lead him readily to a knowledge of the laws which they follow.

Perhaps to this imperfection of method it may be attributed that Natural Philosophy continued to be stationary, or even to decline, during a long series of ages, until little more than two centuries

ago.

Within this comparatively short period it has rapidly reached a degree of perfection so different from its former degraded state, that we can hardly institute any comparison between the two. Before that epoch, a few insulated facts, such as might first happen to be noticed, often inaccurately observed, and always too hastily generalized, were found sufficient to excite the naturalist's lively imagination ; and having once pleased his fancy with the supposed fitness of his artificial scheme, his perverted ingenuity was thenceforward employed in forcing the observed phenomena into an imaginary agreement with the result of his theory; instead of taking the more rational, and it should seem, the more obvious, method of correcting the theory by the result of his observations,

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