The exact knowledge of the heavens, which makes so grand a feature in modern science, is due, however, not only to the existence of instruments, but also to the establishment of observatories especially devoted to their use. The first astronomical observatory that was constructed was that at Paris. In 1667 Colbert submitted the designs of it to Louis XIV., and four years afterwards it was completed. The Greenwich Observatory was established in 1676, that of Berlin in 1710, and that of St. Petersburg in 1725. Since then numerous others have been erected, private as well as public, in all parts of the world, and no night passes without numerous observations being taken as part of the ordinary duty of the astronomers attached to them. CHAPTER IX. THE TERRESTRIAL WORLD OF THE ANCIENTS.--COSMOGRAPHY AND GEOGRAPHY. With respect to the shape and position of the earth itself in the material universe, and the question of its motion or immobility, we cannot go so far back as in the case of the heavens, since it obviously requires more observation, and is not so pressing for an answer. Amongst the Greeks several authors appear to have undertaken the subject, but only one complete work has come down to us which undertakes it directly. This is a work attributed to Aristotle, _De Mundo_. It is addressed to Alexander, and by some is considered to be spurious, because it lacks the majestic obscurity that in his acknowledged works repels the reader. Although, however, it is not as obscure as it might be, for the writer, it is quite bad enough, and its dryness and vagueness, its mixture of metaphysical and physical reasoning, logic and observation, and the change that has naturally passed over the meanings of many common words since they were written, render it very tedious and unpleasant reading.