_Center of Action._--Any one of several large areas of high and low barometric pressure, changing little in location, and persisting through a season or through the whole year; e. g., the Iceland low, the Siberian winter high, etc. Changes in the intensity and positions of these pressure systems are associated with widespread weather changes. _Ceraunograph._--A self-registering thunderstorm recorder. _Chinook_, or _Chinook Wind_.--A foehn blowing down the eastern slopes of the Rocky Mountains over the adjacent plains, in the United States and Canada. In winter, this warm, dry wind causes snow to disappear with remarkable rapidity, and hence it has been nicknamed the “snow-eater.” (Cf. _foehn_.) The “wet chinook” is a wind of a different character, blowing from the Pacific Ocean over the northwestern United States. _Circumscribed Halo._--A halo formed by the junction of the upper and lower tangent arcs of the halo of 22 degrees, when the luminary is about 40 degrees or more above the horizon. As the altitude of the luminary increases, the circumscribed halo gradually assumes an elliptical form and finally merges into the halo of 22 degrees. _Circumzenithal Arc._--A rainbow-tinted halo, often very bright, convex to the luminary and 46 degrees or a little more above it. It is sometimes called the _upper quasi-tangent arc of the halo of 46 degrees_, but the circumzenithal arc and the halo of 46 degrees are rarely seen at the same time. _Cirro-cumulus_; _Cirro-stratus_; _Cirrus_.--Forms of cloud. (See Chapter VI.) _Cistern._--The cup, containing mercury, at the base of a mercurial barometer. _Climatography._--1. Descriptive and statistical climatology. 2. An account of the climate of a particular place or region. _Climatology._--1. The science of climate. 2. A body of knowledge concerning the climate of any place or region; as, “the climatology of Panama.” _Climograph._--A diagram introduced by Dr. Griffith Taylor, of Australia, for showing the mean monthly values of wet-bulb temperature and relative humidity at any place, and for comparing such data as recorded at different places throughout the world; especially with reference to the effects of climate on mankind. Other pairs of elements can be used in constructing climographs: e. g., the dry-bulb temperature and the relative humidity. _Cloud-banner._--A bannerlike cloud streaming off from a mountain peak. _Cloud-burst._--A sudden and extremely heavy downpour of rain; especially one in which the water falls in a continuous stream rather than in drops. The term has been most commonly applied to downpours in mountainous regions. _Cloud-cap._--A caplike cloud crowning (1) a mountain summit, or (2) another cloud, especially a mass of cumulo-nimbus.