Discoverers of the Universe: William and Caroline Herschel (review)

As an historian of astronomy, Michael Hoskin has devoted much of his career to researching, publishing on, and giving presentations about William Herschel and his sister Caroline. Hoskin brings together additional information and stories of the Herschel family and their acquaintances that have not been published before: more than in his other books, this volumes details a family history. Hoskin has dug deeply into archival records in a number of repositories to find correspondence by, to, and about William and Caroline. The storylines are intertwined: Herschel's family life, his musical career, and, of course, his passion for astronomy and telescope-making and Caroline's support role.

The structure of the book's 13 chapters is strictly temporal and divided into periods with coherent themes that Hoskin builds on. The longest period (1707-73) covers William's early years and upbringing, his education and musical career, as well as his move to England from Germany and subsequent negotiations with his brother to have Caroline join him. The following few chapters trace William's discovery of astronomy and of Robert Smith's Opticks and James Ferguson's Astronomy Explained. Herschel took up telescope-making and became proficient at fabricating the optics required. Using his instruments, he began systematic observations and corresponded with other observers. These connections were, after his discovery of Uranus, key to his receiving royal support, a move to Slough as astronomer to the king, who made impromptu, late-night visits for tours of the heavens with William. It was also in Slough that he met his future wife, Mary. Where Hoskin has added to his previously published works is the intertwining of Herschel's family and personal life and a variety of social observations in connection with the Herschels' astronomical careers. This approach adds depth to our understanding of William's and of Caroline's place in the scientific and courtly communities.

Chapter 6, "The Construction of the Heavens" was recounted previously in Hoskin's 1963 book, but here again, by deferring to the archival records he has built a more personal history of Herschel's thoughts on the nature of the cosmos. It is in this period (1783-85) that William seriously takes up the observation of nebulae with the aid of Caroline; his nebula observations form the basis of his most substantive contribution to astronomy. The following chapter discusses Herschel's growing ambition to build larger and larger instruments to find more nebulae. It is here that I would disagree with Hoskin, who frequently comments on Herschel's ability to build first-rate telescopes. My hands-on experience with the mechanical components built by Herschel has shown me that they are the work of a good, but not great, mechanician. William's skills were, I would contend, his ability to fabricate and polish first-rate mirrors and his keen observational abilities—abilities that allowed him to overcome the failings of his telescopes' mechanical construction.

The 9th chapter recounts Caroline's independent efforts to search for comets as part of her work supported by the king. Using a variety of smaller instruments, including those William made especially for her, she discovered eight confirmed comets during her sky sweeps. As a result of her contributions, Caroline garnered the respect of other astronomers, including Nevil Maskelyne, the Astronomer Royal.

William's interests later focused occasionally on geology, and while on trips he would take time to look for and study seashells found in hills. During some of William's tours, Caroline would be left to care for William's son John, born when William was well into his fifties. This connection with Caroline, perhaps more than William's influence, directed John to acquire an interest in astronomy at a young age. As William's health and instruments declined, Caroline and John increasingly took up his work. This again is a section where Hoskin's archival searching and reliance on correspondence adds interest and depth to our understanding...