A catalog of sundials from the Harold C. Ernst Collection of Portable Sundials, and a handy reference book on the subject of portable sundials. The sundial is the most ancient scientific instrument to come down to us unchanged. As such it is deserving of a better position in life than that of an ornament. It has played a vital part in the life of man for many thousands of years, and even today it serves us well where the mechanical watch fails. The authors particularly draw attention to the system of classifying, labeling, and cataloging sundials, described in Chapter II. This is the first attempt to bring order out of confusion in sundials.