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 Phaenomena 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.