cavities in the moon are from ten to seventeen thousand feet in depth, that they are surrounded by a great rampart or wall, a hundred, two hundred, or two hundred and fifty miles round, and that the mountains which rise from the floor of the cavity may be about a mile or a mile and a half high.[1]
His study of the moon's face led him, two years after, to believe that, from his far-off station near Windsor, to which he had then removed from Bath, he was looking down one night into the depths of the boiling crater of a volcano in the moon. A discovery so singular was not a thing to publish till he had full assurance of its accuracy. Four years after, he believed he had obtained evidence sufficient to warrant publication. Others, well qualified to judge, were of the same opinion. Among them was a gentleman from the Göttingen Society, to which Herschel the year before had taken the King's present of a 10-feet reflector. Writing to a friend in Paris, that gentleman says:—
"May 30.
"Sir,—Mr. Herschel has lately made a discovery of the greatest consequence, of which I have had the good fortune to be an eye-witness. He had observed last month, one or two days after the new moon, in the dark part of it, three luminous points. Two of these
- ↑ Moretus is a circular depression 120 kilometres across (80 miles), with an isolated mountain in the centre of nearly 7000 feet in height, the most considerable of its kind on the moon (Atlas Photographique de la Lune, Paris 1898, c. 56). The depths of the cavities are frequently very great, Tycho, for example, 5500 metres, or nearly 18,000 feet (c. 30, c. 55). Some of the mountain masses or tablelands are 5000 metres, 6600, and 7100, judging from the shadows they cast, or 16,000, 21,000, or 28,000 feet (c. 55, 56).
