WEATHER WARNINGS.
The two great Forces of Nature are Gravitation and Heat, which always act in opposition to each other.
Weatheris the result of the action of these forces on matter, and where one form of force is in excess of another, changes are produced which become apparent to our senses, or are indicated by suitable instruments.
The Mattercomposing the earth on which we live is of three kinds—solid, liquid, and gaseous.
The Forceincessantly acting on these is the radiant heat of the sun.
The Resultsof this incessant action are:—
1.Calorification, or Heating, which, besides being appreciable by our senses, is indicated by theThermometer.
2.Evaporation, which alters the weight of the air indirectly, by the diffusion of aqueous vapour through it. This alteration ofweightis indicated by theBarometer, the accompanying increase of moisture being indicated by theHygrometer.
3.Rarefaction, which alters theweightof 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, orPluviometer.
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 theAnemometer.
6.Electrification, producing lightning, thunder, magnetic phenomena, and chemical change, respectively indicated by theElectrometer,Magnetometer, andOzonometer.