The Results of this incessant action are:—
1. Calorification, or Heating, which, besides being appreciable by our senses, is indicated by the Thermometer.
2. Evaporation, which alters the weight of the air indirectly, by the diffusion of aqueous vapour through it. This alteration of weight is indicated by the Barometer, the accompanying increase of moisture being indicated by the Hygrometer.
3. Rarefaction, which alters the weight of the air directly.
4. Condensation, producing fog, dew, rain, hail, and snow; all sufficiently apparent when they occur, but estimated accurately only by the Rain Gauge, or Pluviometer.
5. Motion, producing winds, which we are able to appreciate in the gentle breeze and the awful cyclone, the force and velocity of which are indicated by the Anemometer.
6. Electrification, producing lightning, thunder, magnetic phenomena, and chemical change, respectively indicated by the Electrometer, Magnetometer, and Ozonometer.
I.—CALORIFICATION.
Before considering in detail these results of the action of solar radiation on our globe, an attempt to realize the immensity of this stupendous force will materially aid in the general comprehension of the subject.
The earth is a sphere somewhat less than 8,000 miles in diameter; and if we assume, with the gifted author[[1]] of “The Phenomena of Radiation,”—“that it is about 91,300,000 miles from the sun, and moves around it in a slightly elliptical orbit, occupying rather more than 365 days; that its shape is globular, somewhat flattened at its two extremities; that it rotates upon its own axis in the space of 24 hours, that axis being inclined to the annual orbit at an angle of 23-1/2—if we further assume that solar radiation is of such kind and quantity as it is, we are enabled to account for the total amount of light and heat the earth receives, for the superior temperature and illumination of equatorial regions, as compared with polar, with the gradations of intermediate zones, for the alternation of day and night, and the annual progression of the seasons.