When finished, the object-glass had an aperture of nearly twenty-five inches, and was of much greater power than the eighteen-inch Chicago instrument. The length of the tube was about thirty-two feet. The cast-iron pillar supporting the whole was nineteen feet in height from the ground, and the weight of the whole instrument was about six tons. In preparing this telescope, nearly everything, from its extraordinary size, had to be specially arranged.[10] The great anxiety involved in these arrangements, and the constant study and application told heavily upon Mr. Cooke, and though the instrument wanted only a few touches to make it complete, his health broke down, and he died on the 19th of October, 1868, at the comparatively early age of sixty-two. Mr. Cooke's death was felt, in a measure, to be a national loss. His science and skill had restored to England the prominent position she had held in the time of Dollond; and, had he lived, even more might have been expected from him. We believe that the Gold Medal and Fellowship of the Royal Society were waiting for him; but, as one of his friends said to his widow, "neither worth nor talent avails when the great ordeal is presented to us." In a letter from Professor Pritchard, he said: "Your husband has left his mark upon his age. No optician of modern times has gained a higher reputation; and I for one do not hesitate to call his loss national; for he cannot be replaced at present by any one else in his own peculiar line. I shall carry the recollection of the affectionate esteem in which I held Thomas Cooke with me to my grave. Alas! that he should be cut off just at the moment when he was about to reap the rewards due to his unrivalled excellence. I have said that F.R.S. and medals were to be his. But he is, we fondly trust, in a better and higher state than that of earthly distinction. Best assured, your husband's name must ever be associated with the really great men of his day. Those who knew him will ever cherish his memory." Mr. Cooke left behind him the great works which he founded in Buckingham Street, York. They still give employment to a large number of skilled and intelligent artizans. There I found many important works in progress,--the manufacture of theodolites, of prismatic compasses (for surveying), of Bolton's range finder, and of telescopes above all. In the factory yard was the commencement of the Observatory for Greenwich, to contain the late Mr. Lassell's splendid two feet Newtonian reflecting telescope, which has been presented to the nation. Mr. Cooke's spirit still haunts the works, which are carried on with the skill, the vigour, and the perseverance, transmitted by him to his sons.