XIV.
If it turn out again out of the South to the North East with Rain, and continues in the North East two Days without Rain, and neither turns South nor rains the third Day, it is like to continue North East for two or three months.
The Wind will finish these Turns in three Weeks.
THIS Observation is of the same nature with the former, and is plainly deduced from long experience. Our Author seems to contradict himself in saying that these Winds finish their Turns in three Weeks, but his true Meaning certainly is, that they are \about three Weeks in turning from the South to the North East again. Some very great men have laid it down as a thing certain, that the Variations of the Wind are to be accounted for by the Alteration of the Balance of the Air, occasioned by the different Effects of Heat and Cold; but other Writers again insist very copiously on the Effects which Winds have upon the Air, and thus confound us in a Circle of Causes and Effects, whence it is plain that they do not thoroughly understand the Subject themselves, and therefore it is no Wonder that they are not able to explain it to others.
IN some Parts of the World, and especially between the Tropicks, the Winds are regular, and therefore our Philosophers seem to talk more rationally about them. But in our Northern Countries the Alterations of the Wind are so frequent, sudden, and often so little agreeable to the Season, that such general Reasonings will by no Means serve to explain them. It is however very reasonable to suppose that the same general Cause prevails here as between the Tropics, but with less Certainty, because the Power of the Sun is not so great, and the Determinations of the Winds depend on the Situation of Mountains, Rocks, and Woods, which direct the Air driving against them into certain Courses, so that it is impossible to explain, or indeed to judge of the Course of the Winds till the Country is thoroughly known, and all those Eminences that can affect the Winds are well considered.
FROM these Reflections the Value of our Shepherd's Observations will clearly appear. He was not Philosopher enough to talk in this Style, but by a long and steady Attention he came to know, experimentally, what perhaps few Philosophers, with all their Sagacity, would have been able to have found out.
XV.
S. W. WINDS. After a northerly Wind for the most Part two months or more, and then coming South, there are usually three or four fair Days at first, and then, on the fourth or fifth Day, comes Rain, or else the Wind turns North again, and continues dry.
THIS is likewise a very judicious and very useful Observation, and yet it is not a difficult matter to account for it. It is a common Observation, and a very true one, that there is usually fair Weather before a settled course of Rain. The Winds that bring the dark rainy Clouds that obscure the Sky, and cause dull cloudy Weather, often raise these Vapours to such a height, that they are attracted into the cold Region above our Sight, till being condensed there, they fall down upon us again in Snow or Rain, according to our Author's Observation.
BUT if, after a seeming Tendency to Rain, there follow several Days of fine Weather, it is a certain Indication that the Temper of the Air is altered, and that these Vapours had been driven off before they had time to condense, which is confirmed by the Change of the Wind on such Occasions.