than nominal: this, however, can in no degree diminisă our detestation of the principle of its infliction.

Whilst restricted to his residence at Arcetri, Galileo could hardly venture to direct his attention much to astronomical studies, which, under the circumstances of his case, was both unsafe and could not but carry with it the most unpleasant associations. His mind recurred, therefore, with increased satisfaction to the favourite subject of his earliest enquiries, the doctrine of motion. The fruit of his speculations are presented to us in the "Dialogues on Motion," which were published in 1636; but as all his works, "edita et edenda," were placed by the Inquisition on the prohibited list, there was considerable difficulty in getting it printed. It appeared, however, at Amsterdam.

These dialogues are a continuation of those on the system, and are carried on between the same speakers. They contain the developement of all Galileo's researches on the theory of motion; and form, in fact, the most complete statement of the first principles of dynamics, as far as he had investigated them.

Among the principal topics of discussion, is that of the rectilinear descent of bodies. The author's experiments are related in full detail; but, owing to the imperfection of his methods, he deduced a result differing considerably from the truth. He enters largely into the refutation of the Aristotelian doctrine of the acceleration of a falling body by the air; and investigates the motion of projectiles, showing by distinct and satisfactory reasoning that their path in a vacuum will always be a parabola. In this, as well as some other parts of his researches, he distinctly introduces the great principle of the composition of forces, which he establishes on grounds at least sufficiently general for the purposes of these investigations.

It is somewhat remarkable, that a philosopher of Galileo's penetration should not have entirely rejected the notion of nature's abhorrence of a vacuum. Yet he did not consider a vacuum impossible; for he describes

an experiment in the Dialogues devised for the purpose of forming one. With regard to the pump, he certainly would seem to have still held the theory of suction; which is not only a very extraordinary circumstance in itself, but the more so because he describes an experiment by which he attempted to measure the weight of air as compared with water.

In another part of the Dialogues we have some curious anticipations of the time in which light is transmitted; an account of the vibrations of musical strings, and the coincidence of their pulsations as occasioning harmony; with a description of the original experiment, since so much enlarged upon, of the regular figures assumed by sand strewed on a plate made to vibrate. These subjects, together with that of the strength of beams, comprise the principal materials of these Dialogues.

After the completion of the "Dialogues on Motion," Galileo turned his thoughts again to the method of determining the longitude by the eclipses of Jupiter's satellites, and became involved in a discussion of that and other schemes. Morin, a French philosopher, had proposed, about 1636, a plan, which is, in fact, the same as the method of lunar distances. Galileo raised against it what were, indeed, insuperable objections at that period; the practical impossibility of executing it with the necessary exactness, both from want of tables and instrumental means. Galileo naturally preferred his own method, the practical difficulties of which do not seem to have struck him.

The application of the pendulum to clocks has been a subject of question, as to the priority of invention, between Galileo and Huyghens. We shall here only observe, that Galileo never claimed it; and, upon the whole, there does not appear to us any ground for depriving Huyghens of the credit of it.*

Galileo was now suffering from the increasing infirm ities of age, as well as several severe attacks of illness: yet, such was the inveterate rancour of his persecutors, *The evidence is discussed in Drinkwater's Life of Galileo, p. 98.

that he was for a long time refused permission to go to Florence, with a view to benefit his health; until, in 1638, leave was reluctantly granted, under close restrictions. In a few months, he returned to Arcetri. His sight now began to fail, and he shortly became totally blind. He had, however, occasionally continued to make astronomical observations; and had just noticed the phenomenon of the moon's libration, the last of the long list of his discoveries.

The restrictions of the inquisitors were now so far relaxed that his friends had free access to him; and persons of the highest rank and distinction crowded round him to express their admiration and sympathy, when they found it no longer unsafe. Many eminent men of other countries visited him, among whom we find Milton. Some, indeed, came to Italy for the sole purpose of seeing him, and enjoying his conversation, which retained all its charms.

In addition to his other infirmities, he at length became deaf; yet his intellectual powers remained unimpaired, and he used to complain that he found his head too busy for his body. He was, in fact, entering largely into mechanical speculations, with a view to continuing the "Dialogues on Motion;" but, in the midst of these employments, he was seized with a renewed attack of his complaints, and died January 8th, 1642.

The ecclesiastical powers disputed his will, as being that of a heretic; and at first refused him burial: this was at length permitted, though in a very obscure manner; and no monument was allowed to be erected over him. Medals, however, were struck in commemoration of him by his disciple Viviani. About a century after, a monument was erected in the church of Santa Croce, at Florence.

Lastly, to complete the triumph of bigotry, a collection of his unpublished MSS. in the possession of his family, was subjected to the expurgation of the priests; and even what they suffered to remain in the possession of his grandson, Cosimo, was deliberately committed to

the flames by his own hand, as a pious sacrifice before devoting himself to the life of a missionary.

We cannot better conclude our account of Galileo and his discoveries, than by quoting the able summary of his character and labours given by professor Playfair:

"One forms, however, a very imperfect idea of this philosopher from considering the discoveries and inventions, numerous and splendid as they are, of which he was the undisputed author. It is by following his reasonings, and by pursuing the train of his thoughts, in his own elegant, though somewhat diffuse, exposition of them, that we become acquainted with the fertility of his genius-with the sagacity, penetration, and comprehensiveness of his mind. The service which he rendered to real knowledge is to be estimated, not only from the truths which he discovered, but from the errors which he detected; not merely from the sound principles which he established, but from the pernicious idols which he overthrew. His acuteness was strongly displayed in the address with which he exposed the errors of his adversaries, and refuted their opinions, by comparing one part of them with another, and proving their extreme inconsistency. Of all the writers who have lived in an age which was yet only emerging from ignorance and barbarism, Galileo has most entirely the tone of true philosophy, and is most free from any contamination of the times in taste, sentiment, and opinion.'

By the writings of Copernicus, of Kepler, and Galileo, the solar system, and the subordinate series of truths referring to the theory of motion, were so completely established and unanswerably demonstrated, that nothing was wanting but time to allow the opinions of men to come gradually round to the truth. The determined adherents of the old systems gradually disappeared from the scene, and the younger generation were open to profit by the light now afforded ; and, in a few years, Tycho and Ptolemy had no followers.

Diss. p. 143.

Reception of the new Discoveries by the Church.

The reception which the new philosophy met with among the authorities of the church, is too remarkable a point in this period of its history to be passed over without a brief remark or two.

It might, at first sight, appear, that a religion professing to stand on its own basis, could find little to affect it one way or another in the advance of experimental science; and, above all, a church like that of Rome, reposing on the claim to infallibility, it might be supposed would, of all others, be the last to feel any alarm at researches utterly unconnected with the authority of that claim: but it must be borne in mind, that the pretensions of the Romish church extended to the most unlimited authority over every thing. In particular, the Aristotelian philosophy had long since been incorporated, as it were, into its system; and its speculations were so closely mixed up with the scholastic theology, even to its physical details*, that it constituted almost an integrant part of the creed of the church: any attempt to impugn it was, therefore, heresy.

If we look at the actual treatment experienced by some of the principal advocates of the new discoveries, there is a difference observable which, though at first sight somewhat unaccountable, yet, upon a little consideration, may serve to give us a more instructive insight into the real nature of the case. Copernicus and Foscarinus taught the very same doctrines as Bruno, Kepler, and Galileo; but the former were, as we have seen, received into the highest favour, while the latter were persecuted with unrelenting severity. Yet were they not all equally guilty of heresy, and equally dangerous enemies to religion? Their doctrines were, indeed, the same; but we may have observed a considerable dif

For a full explanation the reader is referred to Dr. Hampden's Bampton Lectures, pp. 191. 334. Oxf. 1833.