A Solar Eclipse Explained

These eighteenth-century diagrams of solar eclipses are from the first major work written by James Ferguson—his book entitled Astronomy Explained Upon Sir Isaac Newton's Principles and Made Easy to Those Who Have Not Studied Mathematics. Ferguson was an entirely self-taught Scottish astronomer who, despite never receiving formal training, became famed for his travelling lectures and easy-to-understand works on the basics of astronomy. Ferguson learned mechanics at a very early age and developed an interest in stargazing while working as a shepherd in the Scottish highlands. These interests, as well as an innate skill for draftsmanship, were encouraged by his father and others but, due to lack of funds, he was unable to pursue study at one of the major universities in Scotland. He supported himself and his family for many years by painting portrait miniatures with India ink.

Astronomy Explained earned him an immediate scientific reputation, resulting in his election as Fellow of the Royal Society in 1763. It provides easy-to-follow illustrated instructions and describes, in clear and accessible language, the movements of the planets, the timings of eclipses, and the discoveries of other astronomers such as Johannes Kepler, Sir Isaac Newton, and Edmond Halley. This was a remarkably useful enterprise: it allowed ordinary people without formal mathematical training to understand the works of Newton and helped support the vogue for amateur astronomy that was taking place in Great Britain during the mid-eighteenth century. Ferguson travelled the country giving popular lectures on astronomy and followed this book with several others along similar themes in the 1760s and 1770s until his death in 1776.

This copy held by Special Collections & Archives is from a later publication of the book in 1811; Ferguson’s work was highly popular and continued to be reprinted during the decades following his death. These illustrations were designed to help the reader understand how a solar eclipse takes place. Figure II illustrates why just a narrow portion of the Earth experiences the total eclipse. Figure III spells out the timing of an eclipse, with a scale of hours and minutes, to show how long it is from the beginning to the end of a total eclipse of the sun at the latitude of London, England.