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When Clouds appear like Rocks and Towers,

The Earth's refresh'd by frequent Showers.

THE Reason of this seems to be, that the watery Vapours are then condensed, or condensing, which gives them this rough and ragged Appearance, and as soon as the thin Films that retain the Water are broke by this Pressure, these heavy Clouds descend in Rain.

THESE Observations, as well as some that follow, are agreeable to all Climates, which is the Reason that they appear in so many different Authors, and have been taken notice of in so many Ages. This however does not at all diminish the Credit, or the Merit of our Shepherd's Observations, who certainly drew them not from Books, but from his own Experience, and therefore their agreeing so well with the Rules of other great Masters, ought to establish his Authority in such Cases as are not supported by alike concurrence from ancient or modern Writers, the Testimony of Nature is always sufficient Evidence.

V.

If small Clouds increase——Much Rain.

THIS and the following Observation cannot well be understood, without giving some Account of Clouds in general. The Atmosphere is supposed to extend itself about five Miles round this Globe of Earth, and within that Space move all kind of Vapours exhaled by the Sun's Force, or protruded by the subterraneous Heat. The ascending of these Vapours into the Air, depends upon many things, and therefore as different as its Causes; for instance, their ascent depends in the first place on the degree of Heat with which they are drawn up or forced out; next upon the Lightness of the Vapours themselves; thirdly, on the Density or Rarity of the Air through which they pass; and lastly, on the Force and Direction of the Winds, which they encounter in their Passage.

ACCORDING to the Nature of these Vapours, and the Circumstance attending their Passage, they appear to us differently below. For if they be extremely subtile they mount very high, and there, according to the Sentiment of Sir Isaac Newton, form by Refraction the Azure, or blue Colour, that over-spreads the Sky in serene Weather. Clouds, while they remain visible, do not rise above the Height of a Mile; and we always observe, that the highest are of a very light Colour, and hardly seen. If, therefore, small Clouds increase, it shews, that the Disposition of the Air is such, as that these Clouds cannot rise therein, either from their own Weight, the want of a protrusive Force, or from the falling of the Wind, which in cloudy Weather is always a Sign of Rain.

VI.

If large Clouds decrease——Fair Weather.

THE same kind of Reasoning accounts very clearly for this Prognostick, since it shews, that the Vapours are either exhaled by the Sun's Heat, or are driven off by Winds, and so resolved into smaller Clouds, capable of ascending higher in the Atmosphere; all which are Circumstances that secure us from Rain, and afford us a certainty of fair Weather.

IT is, however, to be observed, that large black Clouds are frequently, in a Summer Evening, melted into Dews; and this much more frequently happens in the Autumn, because the Evenings are then cooler, and the Vapours more easily condensed for that Reason. In all Observations of this Sort, there is a great degree of Prudence and good Sense required to apply them, and hence it very frequently happens that such Observations are condemned as treacherous and abusive, merely because those who would employ them want the Sagacity which is requisite to understand them clearly.

VII.

MISTS. If they rise in low Ground and soon vanish. } Fair Weather.

THIS is a sure Sign and very well expressed, that is, clearly, and, in few Words, which is the Excellency of such Aphorisms. In order to be convinced of its good Sense and Certainty, we must consider a little what Mists are, whence they rise, and what becomes of them.

MISTS are, strictly speaking, uncompacted Exhalations, which while they fleet near the Earth are styled Mists, but when they ascend into the Air, are called Clouds. If therefore, rising out of low Ground, they are driven along the Plain, and are soon lost to the Sight, it must arise from some of these Causes. That there is an Air abroad sufficient to divide and resolve them, or the Heat of the Sun has been strong enough to exhale them, that is, to rarify them, so as to render them lighter than the Air through which they were to pass. Whichever way this happens the Maxim remains unimpeached.

VIII.

If they rise to the Hill-tops. } Rain in a Day or two.

WHEN Mists are very, heavy in themselves, and rise only by the Action of that protrusive Force, exerted by the subterranean Fire, they can rise no higher than where the Gravitation becomes superior to that protrusive force, for then they descend again by their own Weight, and this occasions the Appearance mentioned in the Observation of their hanging upon Hill-tops, where they are very soon condensed, and fall down in Rain.

THERE was formerly a very idle and ill grounded Distinction between moist and dry Exhalations, whereas in Truth all Exhalations are moist, or in other Words are watery Steams thrown off by Bodies respectively dry, and the former Distinction was invented only to solve these Phænomena of which we have been speaking, that is, the Mist rising and, dispersing without Rain, and the Mist condensed and resolved into Rain, which as I have shewn may be much better explained without any such Distinction.

IX.

A general Mist before the Sun rises, near the full Moon. } Fair Weather.

THIS is a general and a very extensive Observation, which enables us to judge of the Weather for about a Fortnight, and there is very great Reason to believe that it will very rarely deceive us. In order to convince the Reader of this, it will be necessary to explain, as far as we are able, the Causes of this.

MISTS are observed to happen when the Mercury in a Barometer is either very low of very high. They happen when it is high after the Region of the Air has continued calm a good while, and in the mean time a great Abundance of Vapours and Exhalations have been accumulated, making the Air dark by their quantity, and the disorderly Disposition of their parts. They happen when the Mercury is low, sometimes because the Rarity of the Air renders it unable to sustain the Vapours, which therefore descend and fall through it.

BUT none of these Cases agree with the Observation at the Head of the Page, and therefore to form a true judgment of the Weather, we must distinguish between them and the Case which explains the Observation.

X.

If in the new Moon.——Rain in the old.

WHEN Exhalations rise copiously from the Earth into the Region of the Air, and the Air itself is in a proper Disposition, they ascend to a great Height, and continue a long Time before they are condensed, which accounts very clearly and philosophically for the Interval of fair Weather between the rising of these Mists, and their falling down again in Showers. Their ascending about Sun-rise is a Proof that the Air is thin, but at the same time of a Force sufficient to sustain them, since if the Mists were not specifically lighter than the Air itself they could not ascend.

WHEN the Moon is at the full, and such Exhalations rise plentifully, the time necessary for them to float in the Atmosphere, before they are condensed into Clouds and Rain, extends, generally speaking, beyond the Period of that Moon, and therefore the Observation directs us to expect fair Weather.

XI.

If in the old.——Rain in the New.

BUT as it is observed not only in this Climate, but all the World