elegant contrivance, it is difficult to give it the palm over the much later condensing system, with its thousand possible modifications. The number and the value of these improvements entitle their author to the name of one of mankind's benefactors. In all parts of the world a safer landfall awaits the mariner. Two things must be said: and, first, that Thomas Stevenson was no mathematician. Natural shrewdness, a sentiment of optical laws, and a great intensity of consideration, led him to just conclusions; but to calculate the necessary formulae for the instruments he had conceived was often beyond him, and he must fall back on the help of others, notably on that of his cousin and lifelong intimate friend, _emeritus_ Professor Swan,[7] of St. Andrews, and his later friend, Professor P. G. Tait. It is a curious enough circumstance, and a great encouragement to others, that a man so ill equipped should have succeeded in one of the most abstract and arduous walks of applied science. The second remark is one that applies to the whole family, and only particularly to Thomas Stevenson from the great number and importance of his inventions: holding as the Stevensons did a Government appointment, they regarded their original work as something due already to the nation, and none of them has ever taken out a patent. It is another cause of the comparative obscurity of the name; for a patent not only brings in money, it infallibly spreads reputation; and my father's instruments enter anonymously into a hundred light-rooms, and are passed anonymously over in a hundred reports, where the least considerable patent would stand out and tell its author's story.