The despotism of the Russian government could not please the republican born; but circumstances obliged him to endure it till 1741, when he quitted Petersburgh for Berlin on the invitation of Frederic the Great. To the necessity for continual reserve and government of the tongue which was necessary in the Russian capital has been attributed his love of silence and study, which exceeded all that is related of any of his contemporaries. The mother of Frederic, who was as much attached to the conversation of distinguished men as the King himself, could never obtain more than a few syllables from Euler at any one time. On her asking the reason why he would not speak, he is said to have replied, “Madam, I have lived in a country where men who speak are hanged.” Euler remained at Berlin till 1766. In 1761 he lost his mother, who had resided with him for eleven years. During this time he was not considered as having abandoned his Russian engagements, and a part of his salary was regularly paid. When the Russians invaded Brandenburg in 1760, a farm belonging to him was destroyed, but he was immediately more than reimbursed, by the order of the Empress Elizabeth. On the invitation of that princess he consented to return to Petersburgh in 1766. He had for some years suffered from weakness in the eyes; and not long after his return to Russia he became so nearly blind, that he could distinguish nothing except very large letters marked with chalk on a slate. In this state he continued for the remainder of his life; and by constant exercise he acquired a power of recollection, whether of mathematical formulæ or figures, which would be totally incredible, if it were not supported by strong evidence. He formed in his head, and retained in his memory, a table of the first six powers of all numbers up to 100, containing about 3000 figures. Two of his pupils had summed seventeen terms of a converging series, and differed by a unit in the fiftieth decimal of the result; Euler decided between them correctly by a mental calculation[8]. His chief amusement during his deprivation was the formation of artificial magnets, and the instruction of one of his grandchildren in mathematics. His studies were in no degree relaxed by it. In 1771 Euler’s house was destroyed by fire, together with a considerable part of the city. He was himself saved by a fellow-countryman named Grimm, and his manuscripts were also rescued. In 1776 he married the aunt of his first wife. No other event worthy of special notice occurred before his death, which took place suddenly, September 7, 1783. He had been employed in calculating the laws of the ascent of balloons, which were then newly introduced; he afterwards dined with his family and M. Lexell, his pupil, conversed with them on the newly-discovered planet of Herschel, and was amusing himself with one of his grandchildren; suddenly the pipe which he held in his hand dropped on the ground, and it was found that[9] “life and calculation