THERE are a Sort of half wise People, who from the Consideration of the Distances of Things, are apt to treat such Prognostications, as they phrase them, with much Contempt. They can see no Connexion between a Cat's washing her Face, and the Sky's being overspread with Clouds, and therefore they boldly pronounce that the one has no Relation to the other. Yet the same People will readily own that the fluttering of the Flame of a Candle is a certain token of Wind, which however is not discernible by their Feeling; because it lies within the Compass of their Understanding to discern that this Fluctuation of the Flame is caused by the Wind acting upon it, and therefore they are inclined to believe this, though it does not fall actually under the Cognizance of their Senses. But a Man of a larger Compass of Knowledge, who is acquainted with the Nature and Qualities of the Air, and knows what an Effect any Alterations in the Weight, the Dryness, or the Humidity of it has upon all animal Bodies, easily perceives the Reason why other Animals are much sooner sensible of any Alterations that happen in that Element than Men, and therefore to him the cawing of Ravens, the chattering of Swallows, and a Cat's washing her Face are not superstitious Signs, but natural tokens (like that of the Candle's fluttering) of a Change of Weather, and as such they have been thought worthy of Notice by _Aristotle_, _Virgil_, _Pliny_, and all the wisest and gravest Writers of Antiquity. BUT still a few slight and trivial Observations of this Kind, and such as are in the Power of every Man to make, go but a very little Way in furnishing us with a useful Knowledge of the Indications of the Weather. To supply these, and to have constantly at Hand the Means of judging of these Alterations, Men of great Genius have invented, and wonderful Inventions they are! Instruments for measuring the Heat, the Cold, the Weight, the Dryness, and the Humidity of the Air, with great Exactness, and upon these they reason as to the changes of Weather with great Accuracy and Certainty. It would undoubtedly be a great Folly to pretend to question either the Truth of their Observations, or the Usefulness of them: but then we may have leave to consider how far, and to how great a Degree they are useful. The Thermometer measures exactly the Degrees of Heat, but the Air must be hot to such or such a Degree before it is discerned by this Instrument. The barometer indicates the Weight of the Air, and the rising and falling of the Quicksilver expresses the Alterations in its Weight with wonderful Nicety, but then those Alterations are the Cause of this. In like manner the Hygrometer, or Hygroscope, measures the Dryness or the Humidity of the Air very plainly and very exactly, but the Weather must alter, must become dryer or moister than it was, before these Alterations are visible; and therefore, however ingenious, however curious, however useful these