Clouds
formations owing their the evaporation of the sea and other atmosphere. The vapor is supplied from the evaporation of the sea and other water surfaces, under the influence of solar heat, and is diffused through the vapor; when charged with this maximum agency of winds. Air-under a given hold, only a certain amount of invisible vapor; when charged with this maximum amount it is said to be saturated. Should the temperature, under this condition, be lowered, as, for instance, when a current is ascending into colder regions, or exclouds are formed, appearing suspended clouds are formed, appearing suspended at a certain level above the surface. bules unite and are finely precipitated in the form of rain, and, with sufficiently reduced temperature, as snow, or perhaps incipient states of clouds, and when in contact with cold bodies produce, by decontact with cold bodies produce, by de- The whole subject is comprised under the name hygrometry. The forms of clouds The whole subject is comprised under the have been observed to depend greatly on altitude, and have been classified accordingly.
The nomenclature proposed by Howard, at the beginning of the 19th century, is still generally adhered to, owing to its simplicity and appropriateness, though a few minor subdivisions have been added.
He divides clouds into three primary modifications, named cumulus, stratus, and cirrus, with the intermediate composite forms-cumulo-stratus, cirro-stratus, cirro-cumulus, and, lastly, nimbus, or rain-cloud. These varieties, and the conrain-cloud. These varieties, and the conly described as follows: Cumulus-Convex or conical masses, generally resting on a horizontal base of apparently dense (so-called cotton bale); they form in the on a horizontal base of apparently dense lower atmosphere under the influence of ascending heated air, and are most developed during the hottest part of the Consists of continuous horizontal sheets, veloped during the hottest part of the a fine-weather sign, appearing mostly during the night and at no great elevation. It forms dense clouds when mixed with smoke or dust. Cirrus-A lofty