100 GENKRAl.lZATION OF THE PRECEDING TABULAR RESULTS 



rain-fall to tlie south have some connection with them. On the Pacific coast, north 

 of latitude 40°, from Cape Mendocino, whence the trend of the coast changes into an 

 almost northerly direction, the rain-fall abruptly increases to a great amount ; this 

 seems to be due to the influence of the Coast Range of mountains intercepting the 

 moisture swept over that part of the Pacific by the prevailing westerly wind, and is 

 probably also connected with the ocean current along that shore. This influence of 

 the Pacific Ocean on the rain-fall prevails but little beyond the eastern flank of the 

 Cascade Range, but it extends into southern California along the Sieri-a Nevada. 

 Between the meridians of about 100° and 119° the average rain-fall is between 8 and 

 20 inches ; though in the vicinity of the higher mountain ranges, and in some valleys 

 favoi-ed by local circumstances, depending on the direction of the wind and variations 

 of temperature, there are no doubt limited areas of greater amount. These still 

 await development. The driest regions are in Nevada, in western Utah, southeastern 

 California, and southwestern Arizona, to which must probably be added the region 

 of the Llano Estacado. It would be useless to attempt any more detailed description 

 of the results laid down on this chart, as it speaks almost for itself. 



Respecting the charts for the seasons, those showing the rain-fall during the 

 summer (June, July, August) and during the winter (December, January, February) 

 appear somewhat less complex and easier of construction than the charts for the 

 spring (March, April, May) and the autumn (September, October, November.) The 

 former comprise the solstices and periods when the solar heat passes through its 

 maximum or minimum, at which times the atmosphere appears less disturbed ; 

 whereas the latter comprise periods of transition, and thus partake of a mixture of 

 phenomena, which manifests itself in the greater contortions of our curves of equal 

 rain-fall. From a purely scientific stand-point the periods of summer and winter are 

 the more interesting ones, Init those of the spring and autumn are not less valuable 

 to the agriculturist. While the distinction of an eastern and a western part, the first 

 well supplied with, the second deficient in precipitation, holds for each season, the 

 contrast so far changes that in summer the western half becomes still more dry, 

 while in winter its moisture increases ; in fact, we shall find for each area a develop- 

 ment of a dry and of a wet season. We, therefore, proceed to the 



CHART SHOWING THE DISTRIBUTION OF RAIN-FALL FOR THE SUMMER. 



Jt (exhibits the rain-tall l)y curves, for every fourth inch, from 2 to 26 inches ; its 

 leading feature is the development of a maximum rain area in Florida. The rainy 

 season in the peninsula attains its maximum about one month after the sun's greatest 

 northern declination ; during the three summer months as much as 26 inches of rain 

 are precipitated. In great contrast with this, we find the region west of the Rocky 

 Mountains almost devoid of rain, there being not as much as 1 or 2 inches of pre- 



