212 Prcfevfatlon luh'tch Animals have 



togc'tlicr. The obfervatinns refpeijling tlic third clafs I col- 

 letted iiivfelf, 



Firrt, ihcn, refpcfting the prefenlicUion which animals have 

 of ftir dry weather. 



Clear, dry weather ocnerally follows after wet weather, 

 when the atmofphere has hcea freed from the yaj)ours col- 

 lected' in it by their fallino- to the earth in rain. Clouds as 

 well as rain are the means by Vv-hich the air frees itfelt from 

 the eleftric vapours that are coniinually ariiing; and ifthefe 

 again fall down, it appears very natural that animals, whick 

 live chiielly in the open air, llioukl exprefs, by various ex- 

 ternal movements, the eafe with which they, breathe, and 

 perfurm all the vital funftinns. From this principle it feems 

 not difilcuit t-) explain tlic following obfervations : 



The fluttering ui bats in the evenino;, beetles flying about 

 on the highways, and the Iportino of gnats towards funfet, 

 require no explanation. I lli;ill only remark, wh;U is already 

 well known to every obferver, that this prelenfacion is highly 

 ufeful to bats as well as to infects. Every fliower. of rain 

 Tvould render it iinpoflible for them to fly, as their wings 

 are not fccured by any oily matter againit moilture : they 

 would therefore be rendered much heavier by rain, and unfit 

 for flying, and they could not be fo ealily placed again in 

 told.s, which, conlidering the Ilructure of thcfe animals, is 

 abi'ilutely ncceirary, as when they have remained dry. 



'i'he lame principle feems to be applicable to the high 

 flight of larks and fwallows, which perhaps luiflen to the 

 upper regions of the atmofphere becaufe they are freer from 

 vapours and more fuited to iheni, and becaufe the lower re- 

 gions, being more loaded with vapours, aflbrd ihcm Icfs plea • 

 lure than thofe above. The uifefts alfo which they purfue 

 for food take then, perhaps, a higher fliglit. 



The croaking of the green water-frog in ponds I cannot 

 luflieicnily explain; but it feems to exprels the pleafure 

 ariling from the greater quantity of infc6ls then flying about, 

 and v.hich they can catch with more eafe and convenience. 

 But clear dry weather is not fo agreeable to frogs as the re- 

 turn of Vvarm weather. If they make a noife in the time of 

 cold ram, warm dry weather will follow. But if the dry 

 weather proceeds from, raw winds, and if warmth and rain 

 fucceed, their iioife may fxjretel. rain ; and tlierefore Lin- 

 iiaiiis's rule prwdicii pluvmm will lofe nothing of its truth. 

 He feems fo much the more to be right, as more raw thaa 

 warm dry days take place in the climate of Sweden. I have, 

 to my great racouveuicncc. experienced the truth of his afler- 



tion,^ 



