34 



INTRODUCTION. 



of regions at least 12 degrees further south. The difference of the chmate between the east- 

 ern and western parts of Europe in the same latitude, is shown by the fact, that at Moscow, 

 which is in the latitude of Edinburgh, the winter is so inclement, as to render every precaution 

 necessary to guard against it, while at the latter place it is not more severe than at Boston. 



4. Seasons of the Torrid Zone. There are only two seasons in the torrid zone ; the dry 

 and the rainy or wet. The latter prevails in the tropical regions over which the sun is verti- 

 cal, and is succeeded by the dry season, when the sun retires lo the other side of the equator. 

 The rains are produced by the powerful action of a vertical sun, "apidly accumulating vapors 

 by evaporation, which then descend in rains ; this arrangement is wisely adapted to afford a 

 shelter from the perpendicular rays of the sun. In some regions there are two rainy seasons, 

 one of which is much shorter than the other. Nothing equals the majestic beauty of the sum- 

 mer in the torrid zone. The sun rises vertically ; it traverses rapidly the red clouds of the 

 east, and fills the heavens with a light, whose brightness is uuobscured by a single shade. The 

 moon shines here with a more brilhant lustre. Venus blazes with purer and more vivid rays, 

 and the milky way glitters with augmented brightness. To all this we may add the serenity 

 of the air, the luxuriance of vegetation, and the gigantic forms of plants and animals ; all nature 

 more grand and more animated, at the same time, that the seasons are more constant and 

 unvarying. 



5. Seasons of the Temperate Zones. The four seasons which we distinguish in this country, 

 are known only in the temperate zones, which alone are blessed with the varied charms of 

 spring and autumn, the tempered heats of summer, and the salutary rigors of winter. In the 

 part of the temperate zone bordering on the tropics, the climate resembles that of the intertrop- 

 ical regions ; and it is between 40'-' and 60^ of latitude, that the succession of seasons is most 

 regular and perceptible. 



('}. Seasons of the Frigid Zones. Beyond the 60th degree of latitude only two seasons 

 take place ; a long and severe winter is there suddenly succeeded by insupportable heats. The 

 rays of the sun, notwithstanding the obliquity of their direction, produce powerful effects, be- 

 cause the great length of the days favors the accumulation of heat ; in three days the snow is 

 disso'ved, and flowers at once begin to blow. 



7. Winds. Wind is a current of air moving in some particular direction ; the velocity and 

 force of winds are various. The following table shows the degrees of velocity of different winds. 



Velocity. — 4 or 5 miles an hour. J\''ame of the Wind. — Gentle wind, 

 10 to 15 Brisk Gale, 



30 to 35 High wind, 



50 Storm, 

 SO to 100 Hurricane. 

 The utility of winds is very great ; they purify the atmosphere, and dissipate the miasmata 

 exhaled from marshes and stagnant waters. They raise and transport the clouds destined to 

 fertilize the earth. Milhons of seeds, furnished with little pinions, are scattered by them fai 

 and wide, thus extending the empire of vegetation. They propel a vast deal of machinery, 

 and transport ships from pole to pole on the great highway of nations. 



8. Permanent., Periodical.^ and Variable winds. Winds may be divided into three class 

 es ; permanent winds, or those which blow constantly in the same direction ; periodical winds, 

 or those which blow in one direction only a certain part of the year, and variable winds, which 

 are constantly changing their direction. 



9. Trade-winds. The permanent winds blowing constantly between, and a few degrees 

 beyond the tropics, from east to west, are called trade-ivinds. They prevail in the Pacific, 

 Atlantic, and parts of the Indian ocean, to about 30° each side of the equator, being on the 

 north a little from the northeast, and on the south from the southeast. In sailing, therefore, 

 from the Canaries to Cumana, or from Acapulco to the Phihppines, the winds blow so steadily, 

 that it is hardly necessary to touch the sails. 



10. Monsoons. In the Indian ocean to the north of 10° S., and in the seas around Ma- 

 laysia, there prevail periodical winds called monsoons., which blow half the year from one quar- 

 ter, and the other half from the opposite direction ; at the time of their shifting or breaking up. 

 variable winds and violent storms prevail. On the north of the equator a southwest monsoon 

 dIows from April to October, and during the rest of the year a northeast monsoon ; on the 

 south of the equator a southeast wind prevails from April to October, and a northwest wind the 

 other half of the year ,' 



