The Harmsworth Atlas 



Climate in Relation to Commercial Products 



Isotherms are lines of equal l^armtn. connecting places of a corresponding temperature. 



A comparison of the maps on this and the opposite page will 

 show how largely Climatic Conditions determine the distribu- 

 tion and character of Vegetable Life. The climate or average 

 Weather of a region varies according to its Latitude, its Elevation 

 above Sea-Ievel, and its Distance from the Sea. Latitude is the 

 chief Climatic factor. It determines the amount of direct heat 

 received from the sun, and the duration of day and night throughout 

 the year. The hottest regions, therefore, lie within the Torrid Zone, 

 extendmg 22j° N. and S. of the Equator, to the Tropics of Cancer 

 and Capricorn. Somewhere within this zone the sun is always right 

 overhead and, therefore, day and night remain constantly of an 

 equal length. The average annual temperature of the Torrid Zone, 

 is over 70°, and so, where the rainfall is copious, we fmd within it 

 regions of dense, evergreen, tropical forest or jungle, such as those of 

 Central Africa or the basin of the Amazon. North and South of the 

 Torrid Zone, and reaching to the Polar Circles, lie the North and 

 South Temperate Zones. In these Zones the nearer we approach 

 the poles, the colder becomes the climate, and the greater the differ- 

 ence m the range of temperature and the respective lengths of day 

 and night at the opposite seasons of the year. Woodlands and 

 arable lands are generally characteristic of the Temperate Zones but 

 towards their equatorial limits lie vast rainless regions, forming 

 belts of desert, in both northern and southern hemispheres 



The Frigid Zones stretch from the Arctic and Antarctic Circles 

 respectively to the Poles. Regions of low temperature, with lon^ 

 and excessively cold winters, and short, though comparatively warm 

 summers, the ir day and night vary in length, from twcnty^four hours 



CLIMATIC 



at the Polar Circles to six months at the Poles. In the Northem 

 Frigid Zone lie the vast boggy plains, known as Tundra, of Arctic 

 America and Nortliern Asia, frozen the greater part of the year, 

 and only covered during the brief summer by a sparse vegetation 

 of mosses and lichens. 



£/^y(3^i(?;i.— Temperature decreases, at an average rate of 1° 

 with each additional rise of 270 feet above sea-level, and therefore 

 the ascent of a mountainous district brings us to successive zones 

 of climate, similar to those we should meet in a journey from the 

 Equator to the Poles. Thus we find the upper slopes of lofty 

 mountains with an Alpine fiora, corresponding to that of the Arctic 

 Regions, even in the neighbourhood of the Equator. This cooling 

 of the temperature with increasing elevation drains rain-bearing 

 winds of their moisture, and hence mountainous districts are usually 

 regions of the most abundant rainfall. 



The Sea exercises a varied influence upon climate. It is the 

 source whence the moisture of the air, which falls as rain, snow or 

 dew, IS derived. It retains a more constant temperature than land 

 surfaces, and therefore maritime countries, and especially islands, 

 enjoy as a rule a more equable climate than inland regions. Lastly, 

 its surface movements, or warm and cold currents,' tend to raise or 

 lower the temperature. The action of currents in determining 

 climate is well illustrated on the Chart of the January Isotherms, 

 where the remarkable northward bend of the Isotherm of 2,2" is 

 due entirely to the influence of the warm Gulf Stream. 



The diagrams given below the rainfall map on page g represent 

 Rain gauges. 



AVERAGE JANUARY & JULY TEMPERATURE IN FAHRENHEIT DEGREES 



Lender, Napks r...co. ^-f c.p.W Ca,.o Cak.Ua S,.g.pore Yak^k Tok.o S^dne, W.nip.^ N^York^rl^ K^ 



er 



79' 





JanJufy Jai,.july Jan J„\y Jan.J^lj, Jsn.Ju 



53' ^' 



&s- 



. O 



I'j Jam. July 



&S' 



76' 







7 



6 



53" 



-i' 



O 00 00 



%/v^ ^i^V^/ *ia\^ ^\J ^\J W kj' W L^ %i^KJ ^^ M 



Jan. July Jan Jufy Ja-. July J^n Jufy Jan July Jan Jul^ JOn July JanJurl/ ^■"-'-'^J 



8 



