overlooked the wonders of creation which were daily presented to their view.

In the year 1606, Galileo was again appointed to the professorship at Padua, with an augmented stipend of 520 florins. His popularity had now risen so high, that his audience could not be accommodated in his lecture-room; and even when he had assembled them in the school of medicine, which contained 1000 persons, he was frequently obliged to adjourn to the open air.

Among the variety of pursuits which occupied his attention, was the examination of the properties of the loadstone. In 1607, he commenced his experiments; but, with the exception of a method of arming loadstones, which, according to the report of Sir Kenelm Digby, enabled them to carry twice as much weight as before, he does not seem to have made any additions to our knowledge of magnetism. He appears to have studied with care the admirable work of our countryman, Dr Gilbert, “De Magnete,” which was published in 1600; and he recognised in the experiments and reasonings of the English philosopher the principles of that method of investigating truth which he had himself adopted. Gilbert died in 1603, in the 63d year of his age, and probably never read the fine compliment which was paid to him by the Italian philosopher—“I extremely praise, admire, and envy this author.”

CHAPTER II.

Cosmo, Grand Duke of Tuscany, invites Galileo to Pisa—Galileo visits Venice in 1609, where he first hears of the Telescope—He invents and constructs one, which excites a great sensation—Discovers Mountains in the Moon, and Forty Stars in the Pleiades—Discovers Jupiter’s Satellites in 1610—Effect of this discovery on Kepler—Manner in which these discoveries were received—Galileo appointed Mathematician to Cosmo—Mayer claims the discovery of the Satellites of Jupiter—Harriot observes them in England in October 1610.

In the preceding chapter we have brought down the history of Galileo’s labours to that auspicious year in which he first directed the telescope to the heavens. No sooner was that noble instrument placed in his hands, than Providence released him from his professional toils, and supplied him with the fullest leisure and the amplest means for pursuing and completing the grandest discoveries.

Although he had quitted the service and the domains of his munificent patron, the Grand Duke of Tuscany, yet he maintained his connection with the family, by visiting Florence during his academic vacations, and giving mathematical instruction to the younger branches of that distinguished house. Cosmo, who had been one of his pupils, now succeeded his father Ferdinand; and having his mind early imbued with a love of knowledge, which had become hereditary in his family, he felt that the residence of Galileo within his dominions, and still more his introduction into his household, would do honour to their common country, and reflect a lustre upon his own name. In the year 1609, accordingly, Cosmo made proposals to Galileo to return to his original situation at Pisa. These overtures were gratefully received; and in the arrangements which Galileo on this occasion suggested, as well as in the manner in which they were urged, we obtain some insight into his temper and character. He informs the correspondent through whom Cosmo’s offer was conveyed, that his salary of 520 florins at Padua would be increased to as many crowns at his re-election, and that he could enlarge his income to any extent he pleased, by giving private lectures and receiving pupils. His public duties, he stated, occupied him only sixty half-hours in the year; but his studies suffered such interruptions from his domestic pupils and private lectures, that his most ardent wish was to be relieved from them, in order that he might have sufficient rest and leisure, before the close of his life, to finish and publish those great works which he had projected. In the event, therefore, of his returning to Pisa, he hoped that it would be the first object of his serene highness to give him leisure to complete his works without the drudgery of lecturing. He expresses his anxiety to gain his bread by his writings, and he promises to dedicate them to his serene master. He enumerates, among these books, two on the system of the universe, three on local motion, three books of mechanics, two on the demonstration of principles, and one of problems; besides treatises on sound and speech, on light and colours, on the tides, on the composition of continuous quantity, on the motions of animals, and on the military art. On the subject of his salary, he makes the following curious observations:—

“I say nothing,” says he, “on the amount of my salary; being convinced that, as I am to live upon it, the graciousness of his highness would not deprive me of any of those comforts, of which, however, I feel the want of less than many others; and, therefore, I say nothing more on the subject. Finally, on the title and profession of my service, I should wish that, to the title of mathematician, his highness would add that of philosopher, as I profess to have studied a greater number of years in philosophy, than months in pure mathematics; and how I have profited by it, and if I can or ought to deserve this title, I may let their highnesses see, as often as it shall please them to give me an opportunity of discussing such subjects in their presence with those who are most esteemed in this knowledge.”

During the progress of this negotiation, Galileo went to Venice, on a visit to a friend, in the month of April or May 1609. Here he learned, from common rumour, that a Dutchman had presented to prince Maurice of Nassau an optical instrument, which possessed the singular property of causing distant objects to appear nearer the observer. This Dutchman was Hans or John Lippershey, who, as has been clearly proved by the late Professor Moll of Utrecht,[8] was in the possession of a telescope made by himself so early as 2d October 1608. A few days afterwards, the truth of this report was confirmed by a letter which Galileo received from James Badorere at Paris, and he immediately applied himself to the consideration of the subject. On the first night after his return to Padua, he found, in the doctrines of refraction, the principle which he sought. He placed at the ends of a leaden tube two spectacle glasses, both of which were plain on one side, while one of them had its other side convex, and the other its second side concave, and having applied his eye to the concave glass, he saw objects pretty large and pretty near him. This little instrument, which magnified only three times, he carried in triumph to Venice, where it excited the most intense interest. Crowds of the principal citizens flocked to his house to see the magical toy; and after nearly a month had been spent in gratifying this epidemical curiosity, Galileo was led to understand from Leonardo Deodati, the Doge of Venice, that the senate would be highly gratified by obtaining possession of so extraordinary an instrument. Galileo instantly complied with the wishes of his patrons, who acknowledged the present by a mandate conferring upon him for life his professorship at Padua, and generously raising his salary from 520 to 1000 florins.