. Public health and preventive medicine. ernate evaporation and condensation, and to its effect as clouds inmodifying solar and terrestrial radiation. The factors determining the mean temperature of any given place are—(1)latitude; (2) altitude; (3) the ratio ofland to water; (4) proximity to thesea; (5) vegetation ; (ti) aspect ; (7) geology. As regards latitude, the mean temperature diminishes from the equator tothe poles from 82° F. to 2*5° F. As regards altitude, the mean temperaturediminishes about 1° F. for every 300 ft. of ascent, or 1° C. lor every o40 presence of much water and
. Public health and preventive medicine. ernate evaporation and condensation, and to its effect as clouds inmodifying solar and terrestrial radiation. The factors determining the mean temperature of any given place are—(1)latitude; (2) altitude; (3) the ratio ofland to water; (4) proximity to thesea; (5) vegetation ; (ti) aspect ; (7) geology. As regards latitude, the mean temperature diminishes from the equator tothe poles from 82° F. to 2*5° F. As regards altitude, the mean temperaturediminishes about 1° F. for every 300 ft. of ascent, or 1° C. lor every o40 presence of much water and close proximity to the sea moderate theextremes of temperature, owing to the fact that water absorbs and radiates healmuch more slowly than kind. The sea, is really the storehouse of thesummers heat, and its distributer during the winter months. Herbage radiatesheat more rapidly than the hare ground, and thus tench? to render hot climatescooler ; while forests have the same effect, owing to their great evaporating METEOROLOGY 129. .surfaces, and the fact that they .shield the .soil. In the northern hemisphere asoutherly aspect and in the southern hemisphere a northerly aspect are re-spectively the hottest. Clay soils are cold, while rocks and dry sand are hot, asthey contain less yearly range of tem-perature is not observ-able at a greater depththan 40 ft. Isotherms are linesdrawn on a chart throughplaces having equal meantemperatures. Sunshine. — Sun-shine is made to auto-matically record its dura-tion by means of a glasssphere (Fig. 48), soarranged as to focus thesuns rays on a sheet ofcardboard or paper, alongwhich they travel,scorching out their cardboard or paperis divided up into sec-tions corresponding toperiods of time. Twosunshine recorders arethe Campbell-Stokes and the Whipple-Casellas, both acting on this prin-ciple. Another method is by employing photography to obtain a continuousrecord of the existence of sunlight, the impression being
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectprevent, bookyear1902
