PROGNOSTICS CONTINTKD. 



able ; if we consider them as so many hydro- 

 meters and thermometers, consisting of an infi- 

 nite number ot tracheae or air vessels, bv which 

 they have an immediate communicat'on with 

 the air, and partake of it> moisture and heat,c. 

 These trachea? are very visible in the leaf of the 

 scabiose, vine, c. 



Hence it is, that all wood, even the hardest 

 and most solid, swells in uv< ist weaihei ; the va- 

 pours easily insinuating themselves into the 

 pores then of, especially of that which is lightest 

 and driest. And hence we derive a verv extra- 

 ordinary use of wood, VIA. for breaking rocks and 

 mill-stones. The method at the quarries is this : 

 Having cut a rock into a cylinder, they divide 

 that into several lessercylindeis, by makinghoics 

 at the proper distances round the great one : 

 thes? holes they fill wiih so many pieces of sal- 

 low wood, dried in an oven ; which, in moist 

 weather, becoming impregnated with the humid 

 corpuscles of the air, swell; and, like wedges, 

 break or cleave the rocks into several stones. 



The speedy drying of the .surface of the earth, 

 is a sign of a northerly wind and fair weather; 

 and iu becoming moist, of southerly wind and 

 rain. Hence the farmer may be instructed, never 

 to trust a sun-shiny day, while the sui face of 

 the earth continues wet ; and to rely on a change 

 to dry weather, as soon as he observes the mois- 

 ture dried np, even though the appearance of the 

 clouds should not be favourable ; for the air 

 sucks up all the moisture on the surface of the 

 earth, even though the sky Se overcast, and that 

 is a sure sign of fairweaih /; but if tiie earth 

 continues moit, and water s'.ands in shallow 

 places, no trust should be put in the clearest sky, 

 in tli is case it is deer it fu I. 



