262 RELATION OF FOEESTS TO 



America is supplied by the Smithsonian Institution, unencumbered 

 by any theory. The arrangements made by this Institution for col- 

 lecting, collating, reducing, and utilizing meteorological observations 

 are on the most ample scale. 



Towards the close of 1873 I received from Professor Henry a series 

 of rainfall tables, comprising all the observations that have been made 

 in regard to the rainfall in the United States since the settlement of 

 Europeans in the country, and an intimation that they had com- 

 menced a new epoch, and had subsequently to the publication of 

 these tables distributed several hundred rain-gauges in addition to 

 those previously used, and to those which had been been provided by 

 the Government in connection with the signal source ; and three rain 

 charts are given showing, from the material collected in the general 

 table of results, the geographical distribution of rain over the area of 

 the United States, with the average amount fallen during the year, and 

 during the seasons of summer and winter. The first chart exhibits 

 the results from 750 stations, and the others the result obtained from 

 nearly the same number. 



In regard to the general character of the distributions of rain on 

 the average througHoat the year, it is stated, — " The most striking 

 features of the phenomenon of raiu, as delineated on the chart, are 

 the apparent precision and continuity in the law of its distribution, 

 and the great variation or range in its amount. Thus the curve, 

 passing over places where the annual fall amounts to 40 inches, can 

 be followed from New Brunswick, on the Bay of Fundy, to Texas ; 

 the isohyetal line of 36 inches, similarly, runs without interruption 

 from the St. Lawrence Eiver to the mouth of the Rio Grande. The 

 regularity of the curves is sufficiently distinct to mark out everywhere 

 the progression in the deposition of the aqueous vapour. The annual 

 amount varies from four inches in the Yuma and Gila Deserts, at the 

 head of the Gulf of California, to SO^inches aud more on the Pacific 

 Coast in Washington Territory ; on the Gulf Coast 6i inches appears 

 to be the maximum amount, and 48 on the Atlantic Coast. 



" The principal supply of rain over the United States comesfrom the 

 Gulf of Mexico ; its diffused vapour can be traced from the eastern 

 slope of the Kocky Mountains to the Great Lakes ; while the supply of 

 vapour from the Atlantic Ocean is distinctly traceable over that area 

 lying north and east of Virginia. All States and Territories west of 

 the Rocky Mountains receive their supply of rain from the condensed 

 vapours of the Pacific Ocean. 



" There are distinct localities of eutry of maximum rain from each 



