The diamond-shaped pointer is always in focus; focusing for individual eyesight is effected by turning the eye-piece, which is furnished with a scale for readjustment.
In 1893 loss of health and failing eyesight obliged him to give up the active duties of his chair, and a deputy professor being appointed, he went to live in London, where he died on the 15th of March 1897.
In 1838 he communicated to the Academy the details of his apparatus, which utilized the revolving mirrors employed by Sir C. Wheatstone in 1835 for measuring the velocity of the electric discharge; but owing to the great care required in the carrying out of the project, and to the interruption to his labours caused by the revolution of 1848, it was the spring of 1850 before he was ready to put his idea to the test; and then his eyesight suddenly gave way.
In 1880 his eyesight began to fail, and shortly afterwards he was attacked with paralysis.
The Sudanese, moreover, shoot better than the fellahin, whose eyesight is often defective.
In 1847, when his eyesight threatened to fail, which disqualified him for sea service, he was appointed to the ordnance department.
He struggled to free his arms from the invisible bonds, his eyesight darkening until he dropped into unconsciousness.
But Xander's enhanced eyesight was able to see one half of the strange interaction.
In his old age he was blinded by cataract, but recovered his eyesight by the operation of couching.
The strain of the next three years' continuous work undermined his health and his eyesight, and he was compelled to retire from his professorship. During these years he had published works on Plato and Socrates and a history of philosophy (1875); but after his retirement he further developed his philosophical position, a speculative eclecticism through which he endeavoured to reconcile metaphysical idealism with the naturalistic and mechanical standpoint of science.
He taught mathematics at Columbia, and in 1845 was admitted to the bar, but, owing to defective eyesight, never practised.
Windthorst was undoubtedly one of the greatest of German parliamentary leaders: no one equalled him in his readiness as a debater, his defective eyesight compelling him to depend entirely upon his memory.
A temporary loss of eyesight interfered with his canvass, and he was defeated by a small majority (1009), the campaign having been watched with the greatest interest throughout the country.
A successful operation for cataract restored his eyesight in June 1900, and notwithstanding his 81 years he resumed to some extent his former political activity.
He recovered from small-pox in his fourth year with crippled hands and eyesight permanently impaired; and a constitution enfeebled by premature birth had to withstand successive shocks of severe illness.
After Mr Gladstone's brief Home Rule Ministry in 1886 he entered Lord Salisbury's next Cabinet again as Irish secretary, making way for Lord Randolph Churchill as leader of the House; but troubles with his eyesight compelled him to resign in 1887, and meanwhile Mr Goschen replaced Lord Randolph as chancellor of the exchequer.
He would in any case have been incapacitated by an affection of the eyesight, which for a while threatened to withdraw him from public life altogether.
These contractions, however, may prove too great a strain upon the eyesight or the memory, and thus become a hindrance instead of a help. This was apparently the case in Greek, for though the early printers cast types for all the contractions of the Greek MSS.
His constitutional weakness and bad eyesight forced him to abandon medicine, which he had adopted as a career, and in 1855 he returned to King's College as lecturer in English language and literature, a post which he almost immediately quitted for the professorship of modern history.