This beautifully structured book presents the essentials of William and Caroline Herschel's pioneering achievements in late 18th-century astronomy. Michael Hoskin shows that William Herschel was the first observational cosmologist and one of the first observers to attack the sidereal universe beyond the solar system: Herschel built instruments far better than any being used at the royal observatory. Aided by his sister Caroline, he commenced a great systematic survey that led to his discovery of Uranus in 1781. Unlike observers before him, whose telescopes did not reveal them as astronomical objects, Herschel did not ignore misty patches of light. Hoskins points out Herschel's achievement in surveying, cataloguing, and describing them as nebulae and even coming to the correct conclusion that their structure evolved over time, with Newton's gravity being the agent of change. Herschel s surveys established a new astronomy looking at the universe rather than the planets! Michael Hoskins account includes sketches and diagrams from Herschel's manuscripts in the Royal Astronomical Society Archives in which he attempts to delineate the structure of the Milky Way galaxy. While it is well-known that Herschel was a revolutionary in telescope design who constructed the world s largest telescopes, Hoskin also gives the full picture of the man as an entrepreneur who built and traded some 400 telescopes. Hoskin also pays close attention to the role of William's sister Caroline Herschel, who is usually portrayed as a helpmate to her brother. But in fact she became a significant astronomer in her own right.