2. In very hot weather, the falling of the mercury indicates thunder.

3. In winter, the rising presages frost and in frosty weather, if the mercury falls three or four divisions, there will be a thaw. But in a continued frost, if the mercury rises, it will certainly snow.

4. When wet weather happens soon after the depression of the mercury, expect but little of it; on the contrary, expect but little fair weather, when it proves fair shortly after the mercury has risen.

5. In wet weather, when the mercury rises much and high, and so continues for two or three days before the bad weather is entirely over, then a continuance of fair weather may be expected.

6. In fair weather, when the mercury 'falls much and low, and thus

continues for two or three days before the rain comes, then a deal of wet may be expected, and probably high winds.

7. The unsettled motion of the mercury denotes unsettled weather.

8. The words engraved on the scale are not so much to be attended to as the rising and falling of the mercury for if it stand at much rain, and then rises to changeable, it denotes fair weather, though not to continue so long as if the mercury had risen higher. If the mercury stands at fair, and falls to changeable, bad weather may be expected.

9. In winter, spring, and autumn, the sudden falling of the mercury, and that for a large space, denotes high winds and storms: but in summer it presages heavy showers, and often thunder. It always sinks lowest

of all for great winds, though not accompanied with rain; but it falls more for wind and rain together, than for either of them alone.

10. If, after rain, the wind change into any part of the north, with a clear and dry sky, and the mercury rises, it is a certain sign of fair weather.

11. After very great storms of wind, when the mercury has been low, it commonly rises again very fast. In settled fair weather, except the barometer sink much, expect but little rain. In a wet season, the smallest depressions must be attended to; for when the air is much inclined to showers, a little sinking in the barometer denotes more rain. And in such a season, if it rise suddenly fast and high, fair weather cannot be expected to last more than a day or two.

12. The greatest heights of the mercury are found upon easterly and north-easterly winds; and it may often rain or snow, the wind being in these points, while the barometer is in a rising state, the effects of the wind counteracting. But the mercury sinks for wind as well as rain in all other points of the compass.

The observation of these, and other rules which you will collect from experience, will in a short time render you both as "weather-wise," as persons can in truth be, in so variable a climate as this.

APPENDIX

то

VOL. IV.

Of Air, as a Vehicle of Heat and Moisture. Of Rain-Dew-Meteoric Stones.

THE causes which determine the distribution of heat over the earth's surface are, as has been shown in Vol. II. Conversation X. either the direct influence of the solar rays, or the communication of heat by the air, from one part of the earth's surface to another. The first of these depends on the latitude of the place, by which the intensity of the heat and light from the sun, and also the length of the day, are determined. But the intensity of