On tie Natural Hijlory of Guiana. igg 



round refembles the roof of a ftage with an infinity of half dropt cuftalns as far as the eye 

 can reach. In two voyages from Europe, I have met with this tropical fky as far north as 

 Cape Finifterre. It came with a fair wind, which continued with us like a regular trade 

 wind, accompanied with the fame appearance of the clouds till we made the Weft Indies. 

 In running down the trade winds, every one has an opportunity of 'verifying this defcrip- 

 tion, and muft be ftruck with tlie beauties which this (ky prefents at the fetting of the fun. 

 The inliabitants of the lower iflands may alfo be well acquainted with it. In the higher 

 ones, the attradlion of the mountains ever forms fets of clouds of other appearances, as ' 

 being produced by other caufes. With our prefent knowledge of meteorology, hardly any 

 other caufe can be affigned for the phenomena above mentioned, than the conftant equal 

 temperature that every where prevails on the intertropical feas. One analogous faft how- 

 ever may be mentioned ; the exceeding fmall range of the barometer in tlie torrid zone. 

 Does the fame caufe regulate fo exa£lly the height of the clouds, and maintain the uniform 

 fufpenfion of the mercury ? We might almoft fufpeft it did, were it not well known that 

 the barometer varies as little upon continents, and in the vicinity of mountains in thefe 

 regions as elfewhere, though the condenfation of vapours is in fuch cafes much more irre- 

 gular. Upon the continent you will frequently obferve this tropical Iky alfo, efpecially in 

 fine fettled weather ; but much more commonly you will find the Iky there, and even be- 

 fore you make the coaft, covered with heavy large dark clouds in fome places, and in others 

 at a greater height, the ferene dappled fky fo often feen in Europe. 



Winds. — The trade -zmW generally prevails all the day long, and on the fea coaft feldora. 

 fails even at night ; but in lefs than fifty miles up the river it is a dead calm at night, and 

 the breeze is not able to penetrate fo far till towards noon. Still farther up we had whole 

 days of a flark calm, and the heat very intenfe. 



Dews, fogs and temperature. — The dews, following the law which they generally obferve,, 

 are very heavy when and wherever there is but little wind, and the hotter the day and even- 

 ing they fall the more copioufly ; they were of courfe more abundant up the river than 

 near the fea-coaft. The exhalations in the day-time from a hot and mifty country covered 

 with vegetables being very great, the condenfation occafioned by the abfencc of the fun and 

 the cold accompanying that condenfation are in proportion. Near the coaft, the diurnal 

 difference of temperature is but trifling, the conftant trade -wind preferving in the air nearly 

 the fame medium of heat as in the body of the ocean ; but far up the river the range of the 

 thermometer was very great. 1 he heat of the day was intolerable. In the fliade it was 

 frequently above 90". This, when there is no breeze, forces you into the woods for flielter. 

 Towards evening it cools ; during the night the cold increafes, and is greateft about five 

 in the morning. The thermometer would then be from 72° to 74°. The body of tha 

 river being large enough to retain its heat, the evaporation goes on from its furface 

 through the night, and is condenfed into thick fog, which hangs over it, and is feldom dif- 

 perfed before eight or ten next day. While the air was as above in the morning at 72°,. 

 the water along fide gave 80° to 83% and feldom rofe two degrees higher at noon. We 

 had an opportunity of verifying an obfervation made by the few inhabitants who live far up 

 the river Demerary, that, when it feels very cool in the morning before day-break, they 

 are fure of fine weaiher ; when,, on the contiary, it feels warm, they, expes^ rain. ThejR 



fleep, 



