18 WRITINGS OF JOSEPH HENRY. [1855- 



Mountain system, where we think it will be nearly, if not 

 quite, exhausted. East of this ridge, and as it were, in its 

 shadow, there will exist a sterile belt, extending in a north- 

 erly and southerly direction many hundred miles. The 

 whole country also included between the eastern ridge of 

 the Rocky Mountains and the Pacific Ocean, with the ex- 

 ception of the narrow strip before mentioned, will be de- 

 ficient in moisture, and on account of the heat evolved (as 

 before shown) by the condensation of moisture on the ridges, 

 will be at a much higher temperature than that due to lat- 

 itude. This mountain region and the sterile belt east of it 

 occupy an area about equal to one-third of the whole sur- 

 face of the United States, which with our present knowledge 

 of the laws of nature and their application to economical 

 purposes must ever remain of little value to the husbandman. 

 According to this view, the whole valley of the Mississippi 

 owes its fertility principally to the moisture which proceeds 

 from the Gulf of Mexico, and the inter-tropical part of the 

 Atlantic Ocean. The Atlantic Gulf Stream therefore (as 

 already remarked) produces very little effect in modifying 

 the climate of the northern portion of the United States; 

 both on account of the cold polar current which intervenes 

 between it and the shore, and because of the prevalent west- 

 erly wind, which carries the heat and moisture from us, 

 and precipitates them on the coast of Europe. 



5. The influence of the nature of the soil on the climate 

 of a country, may be inferred from its greater or less power 

 to absorb and radiate heat, and from its capacity to absorb, 

 or transmit over its surface, the water which may fall upon 

 it in rain, or be deposited in dew. In the investigation of 

 this part of the subject, the observations of the geologist, 

 and the experiments of the chemist and the physicist must 

 be called into requisition. 



6. In regard to the influence of cultivation on the climate 

 of a country much also may be said, though at first sight 

 it might appear that man, with his feeble powers, could hope 

 to have no influence in modifying the action of the great 

 physical agents which determine the heat and moisture of 



