North America . e of the continent is representedby isotherms, or lines drawn through localities havingthe same average temperature for the year. On the samemap is also shown in blue the average depth of precipita-tion, including both rains and melted snow. On Fig. 24lines are drawn through points having the same averagebarometrical pressure (isobars) for the months of Januaryand July, together with arrows indicating the general direc-tion of the surface winds (hiring each of these in. nit may be considered as representative of the summerand winter seasons. The data shown on these ma
North America . e of the continent is representedby isotherms, or lines drawn through localities havingthe same average temperature for the year. On the samemap is also shown in blue the average depth of precipita-tion, including both rains and melted snow. On Fig. 24lines are drawn through points having the same averagebarometrical pressure (isobars) for the months of Januaryand July, together with arrows indicating the general direc-tion of the surface winds (hiring each of these in. nit may be considered as representative of the summerand winter seasons. The data shown on these maps havebeen compiled mainly from the reports of the weather bu-reaus of Canada, the United States, and Mexico, and indi-cate, at least in a general way. a summary of what is knownconcerning the main meteorological elements which deter-mine the climatic conditions in North America. An exami-nation of these maps will Suggest certain general conclu-sions in reference to the Kading characteristics ol the cli- 17 ?. Fig. 24.—Average barometric pressure and direction of wind forJanuary and July. CLIMATE i/5 mate in various portions of the continent and the changesthey undergo from season to season. Distribution of Heat and Light.—The distribution overthe earths surface of the heat and light received from thesun is not only of fundamental importance as respects cli-mate, but furnishes a part of the essential conditions onwhich depend the presence and distribution of living organ-isms. The heat and light, or more accurately, the radiantenergy of the sun, the full significance of which is probablynot thoroughly understood, we term, for convenience, inso-lation. The intensity and seasonal distribution of insolationare prime factors on which many important results hinge. Owing to the inclination of the axis about which theearth rotates (230 27) to the plane in which the earth travelsabout the sun, or the plane of the ecliptic, the northern endof the axis is turned towards the sun in s
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Keywords: ., bookcentury1900, bookdecade1900, bookidnorthamerica, bookyear1904
