WEATHER is a term used to denote the state of the earth and of the atmosphere with respect to heat or coldness, dryness or humidity, wind, rain, ke.
In some countries the variations of the atmospherical phenomena occur in an order which is nearly constant; and in those regions, pre dictions concerning the weather for several days, and even for months to come, may be made with almost a certainty that they will be verified by the event. On the opposite sides of the chain of the Ghauta, which extends along the western peninsula of India nearly from north to south, the phenomena during each half of the year are constantly and exactly reversed : thus, along the Malabar coast there is a clear sky from September to the following April, and on the coast of Coromandel the fair season continues from April to September; while during each following six months, in the two regions, it rains almost incessantly. Alternations of fair weather and rain also take place regularly in the Interior of Africa; and, according to Humboldt, it rains constantly during five or six months in every year from the coast of Guiana to the Andes. But In insular situations generally, and in Europe and North America particularly, the winds, varying in direction and intenaity according to no constant known law applicable to the purpose, mingle together at intervals of time apparently irregular, the masses of air which abound with vapour raised from the ocean, and thus cause clouds to cover the horizon, and showers of rain, hail, or snow to descend. The wind which is most prevalent at any one place, generally when It begins to blow affords an indication of the kind of weather which may be expected ; but, frequently, no circumstance occurs by which a change from a clear to a cloudy sky, or the contrary, can be predicted even a few hours before its occurrence.
The periodical changes of the moon's phases often coinciding with changes in the phenomena of the atmosphere, it was very natural that the latter should, by ninny persona, be thought to have sonic dependence on the former [Rats, 0°1.929]; an opinion apparently strengthened by
the known fact tlmt the tides of the ocean and atmosphere are produced by the attractions which the moon and Alm exercise on the particles of water and air. It is certain, however, that the influences of the moon In changing the state of the atmosphere are of short duration, and take place gradually according to constant laws : they are consequently quite incompetent to the production of those sudden and irregular changes to which the atmosphere la subject. There are not, however, wanting men who have formed tables In which the probable state of the weather Is stated in connection with the hour of the day or night at which the new and full moons take place; and that which menin to possess most the confidence of persons to whom an anticipation of rain or fair weather Is of importance, Is one which Dr. Samuel Clarke pro fessed to have formed from along series of observations. It is sufficient here to mention that in this table rain is predicted when the new or full moon takes place between noon and 2 r.x., or between 4 and 6 a.m. ; and fair weather is announced when either takes place between 4 and 8 P.m., or between 10 ism. and 2 a.m. An opinion has prevailed that seasons of a like character return io like order after each revolution of the moon's nodes; that is, at the end of every 18 or 19 years, at which ) times the earth and moon are nearly In like situations with respect to the nodes ; hut though seasons distinguished by more or lam than the usual quantities of rain have been observed to return at certain ki tervals, there appears to be no ground for connecting them with that astronomical period. The existence of a " Cycle of Eighteen Years iu the Seasons of Britain," has been maintained by Mr. Luke Howard, in his work having that title; but the validity of the evidence adduced has been subsequently denied by the Rev. L. Jenyns, in a volume on Meteorology.