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140 slowly feeling their way to a fuller knowledge of the "white clouds" they were discovering among the stars. La Caille, when working at a catalogue of about ten thousand stars in South Africa, set down the places of forty-two, which he saw in the telescope. He divided them into three classes; fourteen in which there was no appearance of stars; fourteen which were clearly composed of small stars; and fourteen which combined the characters of both these classes, small stars surrounded or attended by white spots. His labours were published in 1755. Herschel followed at the end of the century, vastly extended our knowledge of these singular objects, and completed the classification which the Frenchman began.

Turning his attention to the broad band of light known as the Milky Way, of which the various nebulæ "seemed to be portions, spread out in different parts of the heavens," Herschel at once solved the puzzle that then divided the astronomical world. Is it the diffused light of innumerable stars, or a shining gas? He describes it as beyond doubt "a most extensive stratum of stars of various sizes"; and "that our sun is actually one of the heavenly bodies belonging to it is as evident." These were two steps forward, but he did not stop with them. He examined that shining zone in all directions with a powerful telescope—a 20-feet reflector—piercing to the borders of its length, breadth, and thickness. He even undertook to count the number of stars he saw. He called this census of stars gauging the heavens. Four years afterwards, he called it analysing them, and spoke of his method as "perhaps the only one by which we can arrive at a knowledge