a magnifying power, only one thousand, had calculated that he could distinguish an object on the moon's surface not more than 122 yards in diameter, it was clear that his son, with six times the power, could see an object there only twenty-two yards in diameter. But, for any further advance in power and light, the way seemed insuperably closed until a profound conversation with the great savant and optician, Sir David Brewster, led Herschel to suggest to the latter the idea of the readoption of the old fashioned telescopes, without tubes, which threw their images upon reflectors in a dark apartment, and then the illumination of these images by the intense hydro-oxygen light used in the ordinary illuminated microscope. At this suggestion, Brewster is represented by the veracious chronicler as leaping with enthusiasm from his chair, exclaiming in rapture to Herschel: "Thou art the man!" The suggestion, thus happily approved, was immediately acted upon, and a subscription, headed by that liberal patron of science, the Duke of Sussex, with L10,000, was backed by the reigning King of England with his royal word for any sum that might be needed to make up L70,000, the amount required. No time was lost; and, after one or two failures, in January 1833, the house of Hartley & Grant, at Dumbarton, succeeded in casting the huge object-glass of the new apparatus, measuring twenty-four feet (or six times that of the elder Herschel's glass) in diameter; weighing 14,826 pounds, or nearly seven tons, after being polished, and possessing a magnifying power of 42,000 times!--a perfectly pure, spotless, achromatic lens, without a material bubble or flaw!