Johnson william a ph d (1 resultados)

Hardcover. Condición: Very Good+. Limited Edition; 1st Printing. B&W Illustrations; Limited to 5000 unnumbered copies. This book is in Very Good+ condition and is lacking a dust jacket. The book and its contents are in generally clean, bright condition. The spine ends of the book covers have some light rubbing and wear. There is some light ground-in dirt to the book covers. The text pages are clean and bright. There is toning to both front and rear inner hinges. "According to Polhem's autobiography, the event that marked the beginning of his career was the successful repair of the unfinished medieval (16th century) astronomical clock designed by Petrus Astronomus at Uppsala Cathedral, which had remained unfinished and broken for more than a century. In 1690 Polhem was appointed to improve upon the current mining operations of Sweden. His contribution was a construction for lifting and transporting ore from mines, a process that was rather risky and inefficient at the time. The construction consisted of a track system for lifting the ore, as opposed to wires; the construction was powered entirely by a water wheel. Human labor needed was limited to loading the containers. Being new and revolutionary, word of Polhem's work reached King Charles XI of Sweden who was so impressed with the work that he assigned him to improve Sweden's main mining operation; the Falun Mine in Dalarna. " (from Wikipedia).…