Clarke's Figure of Earth. Measurement of Earth's polar and equatorial diameters and factors of compression made by Clarke in 1858-66-80. Equatorial diameter 20,926,348 ft., polar diameter 20,855,233 ft., compression 1/294-3. These values are still used in many modern charts.
Clark Russell's Log. Early type of towed log in which speed of ship was indicated by amount of compression in a spring.
Clasp Hook.* Former name for 'Clip hook'.
Classification of Stars. Astronomers group stars according to spectra and temperature. Seven principal groups are O, B, A, F, K, G, M. The temperature of O stars is about 50,000°C. M stars do not exceed 3000°C. This classification is not usually considered by seamen, but is to be found in the unabridged Nautical Almanac.