The publication of Weather Reports in the daily journals must have convinced the most indifferent that much greater importance is now attached to weather phenomena than formerly; and this conviction will be deepened when it is remembered that a Parliamentary grant of £10,000 is annually expended in support of the Meteorological Office and its seven fully organized observatories in this country, while America expends no less a sum than £80,000 annually in the pursuit of weather wisdom; and the leading nations of Europe have also established meteorological observatories in suitable localities. The balloon ascents of Messrs. Glaisher and Coxwell attracted much attention to the instruments used in estimating atmospheric phenomena, and awakened a desire to know something of the functions of a barometer, thermometer, hygrometer, &c., and especially of the classification of those important weather-warners, clouds. These subjects will be found duly noted in their order, and every phenomenon being traced to its source, Solar Radiation, it is hoped that these pages may prove generally acceptable, and be deemed not altogether unworthy of “THE CLERK OF THE WEATHER.” WEATHER WARNINGS. The two great Forces of Nature are Gravitation and Heat, which always act in opposition to each other. WEATHER is 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 MATTER composing the earth on which we live is of three kinds—solid, liquid, and gaseous. THE FORCE incessantly acting on these is the radiant heat of the sun. 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.