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." 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.