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The first of Herschel’s effective twenty-foot telescopes was erected at 19, New King Street, in the summer of 1781. Enclosing a mirror twelve inches in diameter, it far surpassed any seeing-machine that had ever existed in the world. Yet its maker regarded it as only marking a step in his upward progress. A speculum of thirty-feet focus was the next object of his ambition. For its achievement no amount of exertion was counted too great. Its composition was regulated by fresh experiments on various alloys of copper and tin. Its weight and shape were again and again calculated, and the methods appropriate to its production earnestly discussed. “I saw nothing else,” Caroline Herschel tells us, “and heard nothing else talked of but these things when my brothers were together.”ssss1

ssss1In borrowing Miss Herschel’s lively narratives and comments, some obvious slips in grammar and construction have been corrected. Quotations, too, from the writings of Sir William and Sir John Herschel are often slightly abridged.