"My husband now devoted himself entirely to telescope making and optics. But he took in other work. His pumps were considered excellent; and he furnished all those used at the pump-room, Harrogate. His clocks, telescope-driving[6] and others, were of the best. He commenced turret-clock making in 1852, and made many improvements in them. We had by that time removed to Coney Street; and in 1855 the Buckingham Works were established, where a large number of first-rate workmen were employed. A place was also taken in Southampton Street, London, in 1868, for the sale of the instruments manufactured at York." Thus far Mrs. Cooke. It may be added that Thomas Cooke revived the art of making refracting telescopes in England. Since the discovery by Dollond, in 1758, of the relation between the refractive and dispersive powers of different kinds of glass, and the invention by that distinguished optician of the achromatic telescope, the manufacture of that instrument had been confined to England, where the best flint glass was made. But through the short-sighted policy of the Government, an exorbitant duty was placed upon the manufacture of flint glass, and the English trade was almost entirely stamped out. We had accordingly to look to foreign countries for the further improvement of the achromatic telescope, which Dollond had so much advanced. A humble mechanic of Brenetz, in the Canton of Neufchatel, Switzerland, named Guinaud, having directed his attention to the manufacture of flint glass towards the close of last century, at length succeeded, after persevering efforts, in producing masses of that substance perfectly free from stain, and therefore adapted for the construction of the object-glasses of telescopes. Frauenhofer, the Bavarian optician, having just begun business, heard of the wonderful success of Guinaud, and induced the Swiss mechanic to leave Brenetz and enter into partnership with him at Munich in 1805. The result was perfectly successful; and the new firm turned out some of the largest object-glasses which had until then been made. With one of these instruments, having an aperture of 9.9 inches, Struve, the Russian astronomer, made some of his greatest discoveries. Frauenhofer was succeeded by Merz and Mahler, who carried out his views, and turned out the famous refractors of Pulkowa Observatory in Russia, and of Harvard University in the United States. These last two telescopes contained object-glasses of fifteen inches aperture.