DOLLOND, JOHN, a distinguished optician, inventor of the achromatic telescope, was descended from a French refugee family, and b. in London, June 10, 1706. His father was an operative Silk-weaver, in humble circumstances, and D. was also brought up to that occupation: Engaged at the loom all day, he devoted great part of the night to his favorite studies of mathematics, optics,. and astronomy. Not content with these, lie turned his attention to the most varied subjects, made himself acquainted with anatomy, and even theology, and went so far in the, study of the classical languages as to translate the Greek Testament into Latin. French, German, and Italian also, he knew well.. He apprenticed his eldest son, Peter, to an optician; and after the, latter had established himself in business on his own account, he was joined by his father in 1752. John D.
now devoted himself to the improvement of the dieptric telescope, in which lie was encouraged by the most distinguished scientific men of the time. After a series,of well= contrived expeliments and researches, carried on for several years, he succeeded in con structing lenses that produced images without any colored fringe. See. ACHROMATIC. This was undoubtedly the greatest improvement that the telescope had received since its first invention. The memoir (published in the Philosophical Transactions for 1758) in which he gave an account of his investigations, was rewarded by the council of the royal society with the Copley medal. In 1761, D. was elected a fellow of the royal society; his death took place on the 30th of Nov. of the same year. His two sons continued to carry on the business with great reputation and success.