Page:Sir William Herschel, his life and works (1881).djvu/144

122 into working order was a serious tax; it required more assistants than his twenty-foot telescope, and he says, "I have made it a rule never to employ a larger telescope when a smaller will answer the purpose."

It still remains as a remarkable feat of engineering and an example of great optical and mechanical skill. It led the way to the large reflectors of Lord, some sixty years later, and several of the forty-foot telescopes of the present day even have done less useful work. Its great feat, however, was to have added two satellites to the solar system. From the published accounts of it the following is taken:

"When I resided at Bath I had long been acquainted with the theory of optics and mechanics, and wanted only that experience so necessary in the practical part of these sciences. This I acquired by degrees at that place, where in my leisure hours, by way of amusement, I made several two-foot, five-foot, seven-foot, ten-foot, and twenty-foot Newtonian telescopes, beside others, of the Gregorian form, of eight, twelve, and eighteen inches, and two, three, five, and ten feet focal length. In this way I made not less than two hundred seven-foot, one hundred