This is a clear, straightforward, informative, and enjoyable venture into one aspect of astronomy and its history.

This "How did we find out ..." series is over all very good, but this subject fits especially well within the framework.

I was a bit disappointed that there was no discussion of the discovery of Uranus, originally misidentified by Herschel as a new comet. Previously I had believed that there were so many comets then that a new one was no big deal, but now I realize that, while the discovery of a new planet is certainly more significant, a new comet would have been worth a paper.

Chapter 1: Ancient sitings of comets, etymology of the word, the direction in which the comet's tail points.

Chapter 2: Tycho Brahe attempts to measure distance to comet using parallax; comet is too far away for this technique to work. Kepler identifies planetary orbits as elliptical, comet orbits are more eccentric than planetary orbits.

Chapter 3: Halley uses Newton's thoughts about gravitation to predict the return of the comet named after him.

Chapter 4; Anders Jean Lexel discovers a new comet with a short period that had not been seen before. The comet never comes back, the hypothesis is that it is yanked out of its orbit by Jupiter. Then in 1818 Johan Franz Encke discovers a new comet with a very short period. It is observed that comets disintegrate very fast, each visit to the sun reducing its size by removing its coma.

Chapter 5: Biela's comet, with a short period, so that its disintegration at every perihelion could be observed and recorded. The relationship of comets to meteors.

Chapter 6: The Oort cloud, birthplace of comets, and Whipple's ideas about comet composition. The solar wind is what forms and directs the comet's tail. Comet Kohoutek, which reached perihelion in 1973. Short speculation about future comet and investigation of their composition, which was pretty much on the money when Halley's comet returned in 1986. ( )