OF THE RIVKR SAINT LAWRENCE. 



271 



slope of the Coast range of mountains, giving rise to the equal summer temperature so 

 frequently described as prevailing on that coast. 



Were the whole of North America, from the; Atlantic to the Pacific, a continuous plain, 

 and were the surface diversified merely by eminences of comparatively small elevation, the 

 moisture from the Pacific would be carried into the interior, and a much greater degree of 

 fertility in the western portion of the Valley of the Mississippi would exist. In the actual 

 condition of the continent, however, the westerly wind which passes over the great moun- 

 tain system which extends from north to south, along the western portion of the conti- 

 nent, deposits its moisture principally on the western slope of the Coast range, and gives 

 fertility and mild climate to California., Oregon, Washington Territory, and to Van- 

 couver's Island, and the British possessions further north. Such moisture as may remain 

 is precipitated on the western slopes of the high ridges of the Rocky Mountains, further 

 east ; and the air becomes almost completely desiccated, leaving the elevated plains east of 

 the Pocky Mountains an arid region, and so deficient in moisture as to be unfit for culti- 

 vation, unless by the; aid of irrigation. Such is the united testimony of all those who 

 have returned from the exploration of the open country between and away from the 

 streams which occasionally form little oases in the great desert. 



So remarkably is this the case, that it has been stated in general terms that if a prime 

 vertical line be drawn from about the longitude of ninety-eight degrees west, striking the 

 Gulf of Mexico, we divide the continent of North America into two nearly equal portions ; 

 that to the east being the cultivated and valuable agricultural portion of the country, — that 

 which lies to the west, with the exception of a few isolated spots, and with the exception, 

 also, of the western slopes of tin; Coast range of the Rocky Mountains, being, for the most 

 part, an arid wilderness. 



It is considered that there are two great systems of wind prevailing over the United 

 States, — the upper from the northwest, and the lower from the southwest; the latter 

 carrying the moisture from the Gulf of Mexico and the Caribbean Sea over the whole of 

 the eastern States of the Union, and the eastern part of the Valley of the Mississippi, 

 and being, therefore, the principal fertilizing wind of the interior of the continent. 

 Were the earth at rest, this wind would ilow directly northward, and would divide its 

 vapor over the whole of the interior of the country, to the base of the Rocky Mountains ; 

 but on account of the rotation of the earth it is drawn eastward, and bears its moisture in 

 a northeasterly direction, leaving a large space, as it were, under the lee of the Rocky 

 Mountains, greatly deficient in this element of vegetable production. 



A small map is appended to this paper, showing tire general direction of the winds. 

 The green portions of the map indicate the naturally woody regions of the country, well 

 supplied with water from the fertilizing winds. The pink-shaded parts indicate rich, 



