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from a diminution of the fpring, or elaftic force of I mingle with the clouds above them, then they caufe 



Rain in very large drops, and this may- happen in 

 ftill fultry weather, for then the clouds, which are 



the air. 



This elallicity, which depends chiefly or wholly upon 

 the dry terrene exhalations, being weakened, the at- 

 inoiphere finks under its burden, and the clouds fall 

 upon the common principle of precipitation. 

 ISow the little veficulie, by any or all of thefe means 

 being once upon the defcent, will perfift therein, not- 

 withitanding the increafe of refiftance they every mo- 

 ment meet withal in their progrefs through ftill den- 

 fer and denier parts of the atmofphere. 

 For as they all tend towards the fame point, viz. the 

 center of the earth, the farther they fall, the more 

 coalitions will they make ; and the more coahtions, 

 the more matter there will be under the fame furface, 

 the furface not only increafing as the fquares, but the 

 folidicy as the cubes ; and the more matter under the 

 fame furface, the lefs fri(5tion or refiftance there will 

 be to the fame matter. 



+ 



Thus, if the cold, the wind, &c. happen to aft early 

 enough to precipitate the veficula?, ere they arc ar- 

 rived to any confiderable height, the coalitions being 

 few in fo fhort a defcent, the drops will be propor- 

 tionably fmall, and thus is formed what we call dew. 

 If the vapours prove more copious, and rife a little 

 higher, we have a mift or fog. 

 A little higher ftill, and they produce a fmall Rain. 

 If they neither meet with cold or wind enough to con- 

 denfe or diflipate them, they form a heavy, thick, dark 

 iky, which laft fometimes feveral daiys or weeks. 

 Hence we mayaccount for many of the phasnomena of 



the weather, e. g. Why a cold is always a wet fum- 

 mer, and a warm a dry one, becaufe the principle of 

 precipitation is had in the one cafe, and wanting in the 



other: ":" ; '■ : V 



Why we'have ordinarily moft Rain about the equi- 

 noxes, becaufe the vapours arife more plentifully than 

 ordinary in the fpring, as the earth becomes loofened 

 ^ from the brumal conftipations, and becaufe, as the 

 1 fun recedes from us in autumn, the cold increafing, 

 [.,. the vapours that had lingered above, during the fum- 

 mer heats, are now difpatched down. 

 Why a fettled, thick, clofe fky feldom ever rains, 

 till it has been firft cleared, becaufe the equally con- 

 fufed vapours muft firft be condenfed and congregated 

 / into,.feparate clouds to lay the foundation of Rain, by 

 J. which means the reft of the face of the heaven is left 

 \. open, ancl pervious to the rays of the fun, &c. ; ? > 

 ' Monf Le Clerc obferves, that all winds do not'pro- 

 duce Rains,, but only fuch as collefta great quantity 

 _ of vapours. - Thus in Holland weft winds are rainy, 

 becaufe they come from tlie oc^an, and blow up the 

 , vapours ; eaft winds blow clear, becaufe they come 

 . over vaft trafts of land 5 north winds are rainy, be- 

 caufe they come from the north fe^, but not fo ratny 

 ...as the weft, becaufe the cold north doth not yield fuch 

 a quantity of vapours as the kinder climate of the 

 „ Britannic ogean ; fouth winds bring Rain too, for 

 that they, dOnfiftiri'g of vapours raifed by the heat of 

 , the fun in a hot quarter, and fo being elevated above 

 others in the air, feem to lie upon our clouds, and 

 , prefs them down towards the earth. 

 Again : Rail) may be produced after this manner. If 



the vapours rife in fo great abundance as to reach and 



over our heads, have no fenfible motion, and in the 

 mean time the heat fills the air wnth vapours, which, 

 joining with the clouds, and fo being ftopped in their 

 progrefs, open a paflage for the ftores in the clouds 

 to defcend upon the earth. 



Sometimes alfo the warm wind thaws the clouds into 

 drops, as we fee fnow difiblved by heat ; now by how 

 much the thicker and fooner any fuch cloud was ga- 

 thered, the larger are the drops that come from "it, 

 becaufe a greater ftore of vapours was condenfed 

 there. From thence it is, that in fummer time we 

 have fudden fiiowers of Rain in very large drops. 

 It ought alfo to be remembered, that in thofe coun- 

 tries which lie between the tropics, where they have 

 the fun vertical, the Rain pours down for feveral weeks 

 together more like pailfuls than drops. And it is ve- 

 ry probable that this is the caufe -, viz. becaufe at that 

 time the fun draws up abundance of vapours, and ra- 

 refies, them extremely, fo that they are elevated as high 

 as poffible, and then are precipitated at once, being 

 too copious and heavy to hang in the air; and befides, 

 there may fometimes be a concurrence of neighbour- 

 ing vapours, which will be ready to croud into that 

 part of the air, which is moft rarefied by the heat of 

 the fun meeting with the vapours, which are raifed 

 in that place, and produce very great clouds and 

 Rain. 



If any afk. How the drops of falling water come to 

 be round, as in Rain ? it is anfwered. That this does 

 not happen by any difpofition peculiar to the water, 

 but becaufe the drops are equally prefixed by the air . 

 on every fide, and thereby forced into a round figure, 

 the refiftance of the air being equal every way ; but 

 others give other reafons for it. 

 In Rain there are two diftinft properties or ipecies ; 

 the one which ferves for the diflblution of the falts of 

 the earth, and the other is a terreftrial matter, which 

 it meets with in its fublimation, which may with fomc 

 propriety be called either fait or nitre, and both thefe ' 

 are ufeful in the bufinefs of vegetation. 

 Rain is operative in diflblving the falts that are in the 

 earth, and cools and bathes the cortex or fkin of all 

 vegetables, and, by a fort of relaxation, caufes the 

 fap to pafs up more. freely, and by that means to 

 grow, and ftioot tlie better. . . -. ' 



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'k t 



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,hele loggy humid vapqprs anting out ot the ground, 

 &c. of which Rain is formed, would inevitably ftas- 

 nate and poifon the whole face of the earth, were- 

 they not fublimated by the air, and drawn up by the 

 affiftance of the fun into the upper regions, but, be- 

 ing there rarefied, they are made of fecond ufe in 

 vegetation. ^ "' * , '-' ' " 1 -? ' : - ' ' : 

 As to the quantity of Rain that falls, its proportion" 

 in feveral places at the fame time, and in the fame 

 place at feveral times, we have ftore of obfefvatlons, 

 journals, &c. in the Memoires of the Frwich Acade- 

 my, the Philofophical Tranfaftions, &c. an idea of 

 which take as follows : 



Upon meafuring then, the Rain falling yearly, its 

 depth, at a medium?, is found as, in the following 

 table : > ^ . ^ 



- * 



• - 





,-} Wi . -, 



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