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 1847, when his eyesight threatened to fail, which disqualified him for sea service, he was appointed to the ordnance department.
In 1880 his eyesight began to fail, and shortly afterwards he was attacked with paralysis.
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