WEST WINDS consist of air brought hastily from the south, and checked from proceeding further to the north by a beginning production of air in the northern regions, warm and moist, generally succeeded by north-east wind. 2. They consist of air bent down from the higher regions of the atmosphere, if this air be from the south, and brought hastily it becomes a wind of great velocity, moving perhaps 60 miles an hour, is warm and rainy; if it consists of northern air bent down it is of less velocity and colder. _Application of the preceding Theory to Some Extracts from a Journal of the Weather._ _Dec. 1, 1790._ The barometer sunk suddenly, and the wind, which had been some days north-east with frost, changed to south-east with an incessant though moderate fall of snow. A part of the northern air, which had passed by us I suppose, now became retrograde before it had acquired the velocity of the earth's surface to the south of us, and being attended by some of the southern air in its journey, the moisture of the latter became condensed and frozen by its mixture mith the former. _Dec. 2, 3._ The wind changed to north-west and thawed the snow. A part of the southern air, which had passed by us or over us, with the retrograde northern air above described, was now in its turn driven back, before it had lost the velocity of the surface of the earth to the south of us, and consequently became a north-west wind; and not having lost the warmth it brought from the south produced a thaw. _Dec. 4, 5._ Wind changed to north-east with frost and a rising barometer. The air from the north continuing to blow, after it had driven back the southern air as above described, became a north-east wind, having less velocity than the surface of the earth in this climate, and produced frost from its coldness. _Dec. 6, 7._ Wind now changed to the south-west with incessant rain and a sinking barometer. From unknown causes I suppose the quantity of air to be diminished in the polar regions, and the southern air cooled by the earth's surface, which was previously frozen, deposits its moisture for a day or two; afterwards the wind continued south-west without rain, as the surface of the earth became warmer. _March 18, 1785._ There has been a long frost; a few days ago the barometer sunk to 291/2, and the frost became more severe. Because the air being expanded by a part of the pressure being taken off became colder. This day the mercury rose to 30, and the frost ceased, the wind continuing as before between north and east. _March 19._ Mercury above 30, weather still milder, no frost, wind north-east. _March 20._ The same, for the mercury rising shews that the air becomes more compressed by the weight above, and in consequence gives out warmth.