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 _éclat_, frequently to one thousand persons (scarcely less than what Abélard 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.