Christopher Polhem was the first of great Swedish engineers and inventors. He was born at the ancient town of Visby, in the island of Gothland, in 1661, and was the son of a merchant, who died when Christopher was a child. When only twelve years of age he had to make his own living. As secretary to a widow of wealth, he early developed his genius as a mechanician, building his own shop of carpentry, sloyd, etc., making watches and devising smaller inventions. His want of a classical education was detrimental to him, and he commenced, when twenty-four years of age, to study Latin with various ministers in the country, in exchange for works of his genius and handicraft. At last he was able to enter the University of Upsala by means of recommendations from his last teacher. Soon after his arrival he created considerable attention and admiration by a proof of his ingenuity. Behind the high altar in the Upsala Cathedral there was a clock of the finest workmanship, devised in mediæval times by a monk of the monastery of Vadstena. It was out of order, and not for a hundred years had anybody attempted to set it right. Polhem undertook to reconstruct the whole work, connecting with the main mechanism all the hands which pointed out the hours of the day, the eclipses of the moon and the motions of the “ruling” planets, according to the system of the astrologers. Polhem succeeded in his task, and was allowed to test his invention of automatic haulers of ore in the mines. The college of mining, before which the invention was successfully demonstrated, accepted it, and Charles XI. appointed Polhem a mining engineer. In 1694, Polhem made an extensive journey through England and the Continent. In Paris he learned that several mathematicians were in vain endeavoring to construct a clock which would simultaneously show the time of the day in various countries and strike the hours at the same time. Polhem announced through the Swedish ambassador in Paris that he was willing to solve the problem. He constructed a model which gave universal satisfaction. Louis XIV. had a clock made after this model and gave it as a gift of honor to the Turkish sultan. Upon his return he proposed the founding of a _laboratorium mechanicum_, which in several respects served as a pattern for the later technological institutes of Stockholm and Gothenburg. The youthful Charles XII. embraced the idea with interest, but the promising institution came to a standstill during the wars. Among Polhem’s more remarkable inventions was one for the leading of water-power, to be used at considerable distances. Charles XII. said that a man like Polhem was not to be had for several centuries, and that for this reason he ought to be made useful as long as he lived. A task of gigantic proportions was intrusted to him--the construction of a dock for the navy yards at Carlskrona. The great engineer filled it in an admirable way, and was appointed councillor of commerce and