n hydrostatics, he set forth the true principle of flotation. He invented a thermometer, though a defective one, but he did not, as is sometimes claimed for him, invent the microscope. Though, as has been said, it is by his astronomical discoveries that he is most widely remembered, it is not these that constitute his most substantial title to fame. In this connection, his greatest achievement was undoubtedly his virtual invention of the telescope. Hearing early in 1609 that a Dutch optician, named Lippershey, had produced an instrument by which the apparent size of remote objects was magnified, Galileo at once realized the principle by which such a result could alone be attained, and, after a single night devoted to consideration of the laws of refraction, he succeeded in constructing a telescope which magnified three times, its magnifying power being soon increased to thirty-two. This instrument being provided and turned towards the heavens, the discoveries, which have made Galileo famous, were bound at once to follow, though undoubtedly he was quick to grasp their full significance. The moon was shown not to be, as the old astronomy taught, a smooth and perfect sphere, of different nature to the earth, but to possess hills and valleys and other features resembling those of our own globe. The planet Jupiter was found to have satellites, thus displaying a solar system in miniature, and supporting the doctrine of Copernicus. It had been argued against the said system that, if it were true, the inferior planets, Venus and Mercury, between the earth and the sun, should in the course of their revolution exhibit phases like those of the moon, and, these being invisible to the naked eye, Copernicus had to change the false explanation that these planets were transparent and the sun's rays passed through them. But with his telescope Galileo found that Venus did actually exhibit the desired phases, and the objection was thus turned into an argu...
