This book describes a history of clocks and watches, with emphasis on their use at sea for determining longitude.
It traces the technical development in time-keeping instruments from Sun-dials and sand-glasses; through the earliest mechanical clocks and watches; the works and times of Harrison, Berthroud, Le Roy, etc. and the Board of Longitude; to more recently invented mechanisms, focussing on the mechanisms themselves rather than their inventors. Finally, there is a section describing the modern marine chronometer and its use.
This book is very well written, with diagrams and descriptions which should make sense to anyone with a modicum of mechanical understanding. The only criticism is in some of the references to the photographs, which in places do not match; the subject of the photograph being not that of the text.