In 1855 Mr. Cooke obtained a silver medal at the first Paris Exhibition for a six-inch equatorial telescope.[8] This was the highest prize awarded. A few years later he was invited to Osborne by the late Prince Albert, to discuss with his Royal Highness the particulars of an equatorial mounting with a clock movement, for which he subsequently received the order. On its completion he superintended the erection of the telescope, and had the honour of directing it to several of the celestial objects for the Queen and the Princess Alice, and answered their many interesting questions as to the stars and planets within sight. Mr. Cooke was put to his mettle towards the close of his life. A contest had long prevailed among telescope makers as to who should turn out the largest refracting instrument. The two telescopes of fifteen inches aperture, prepared by Merz and Mahler, of Munich, were the largest then in existence. Their size was thought quite extraordinary. But in 1846, Mr. Alvan Clark, of Cambridgeport, Massachusetts, U.S., spent his leisure hour's in constructing small telescopes.[9] He was not an optician, nor a mathematician, but a portrait painter. He possessed, however, enough knowledge of optics and of mechanics, to enable him to make and judge a telescope. He spent some ten years in grinding lenses, and was at length enabled to produce objectives equal in quality to any ever made. In 1853, the Rev. W. E. Dawes--one of Mr. Cooke's customers--purchased an object-glass from Mr. Clark. It was so satisfactory that he ordered several others, and finally an entire telescope. The American artist then began to be appreciated in his own country. In 1860 he received an order for a refractor of eighteen inches aperture, three inches greater than the largest which had up to that time been made. This telescope was intended for the Observatory of Mississippi; but the Civil War prevented its being removed to the South; and the telescope was sold to the Astronomical Society of Chicago and mounted in the Observatory of that city. And now comes in the rivalry of Mr. Cooke of York, or rather of his patron, Mr. Newall of Gateshead. At the Great Exhibition of London, in 1862, two large circular blocks of glass, about two inches thick and twenty-six inches in diameter, were shown by the manufacturers, Messrs. Chance of Birmingham. These discs were found to be of perfect quality, and suitable for object-glasses of the best kind. At the close of the Exhibition, they were purchased by Mr. Newall, and transferred to the workshops of Messrs. Cooke and Sons at York. To grind and polish and mount these discs was found a work of great labour and difficulty. Mr. Lockyer says, "such an achievement marks an epoch in telescopic astronomy, and the skill of Mr. Cooke and the munificence of Mr. Newall will long be remembered."