CLIMATIC CHANGES IN THE PRAIRIE REGION. 297 



returned to the atmosphere. Ammonia, another important constituent in the life 

 of a plant, results from the decay of animal matter, and is taken up by the 

 atmosphere, from whence it is returned to the soil in the rain and snow, it is then 

 absorbed by the earth and taken up by the plant, which separates it into its ele- 

 ments, one moiety of which enters into the formation of the wood and the other 

 into the gluten. 



Humus, or black mould, the evidence of fertility in soils, is decayed vege- 

 table matter ; when the earth is plowed up the underlying humus is brought in 

 contact with the air and a fresh supply of carbonic acid is supplied. Humus is 

 the source of vegetable production in every soil, and the impoverishment of land 

 is principally owing to the removal of the annual product without the return of 

 an equivalent. Where the vegetable matter is allowed to decay on the soil, its 

 richness is constantly increased, and the result, for long periods, is the mighty 

 fertility of the virgin lands of the great West. 



There is hardly any portion of the great Plains where the soil is not suffi- 

 ciently rich to meet all the requirements of vegetable life in a remarkable de- 

 gree ; the accumulation of humus by the early decay of the luxuriant grasses that 

 have carpeted them for centuries has given them a soil of the highest agricultural 

 possibilities. 



Lime, in some of its combinations, constitutes as an essential engredient in 

 all the more valuable cereals, both grain and grasses. Its presence in the soil is 

 consequently to be considered as a condition of fertility. It has a powerful ten- 

 dency to augment the consolidation and tenacity of land, and its power of retain- 

 ing water. It also promotes the putrefaction and decomposition of humus, and 

 the reciprocal action of the fluids or nutritive juices contained in the soil, and 

 imparts its carbonic acid to the humus, or even to the plant itself. 



The hull or epidermis enveloping the farinaceous portions of grain grown on 

 soil in which there is a due admixture of calcareous matter, and the farina itself 

 is much greater in quantity and richer in quality than in grain grown on lands 

 which exhibit a deficiency of this earth. 



The excellent quality of the wheat grown to day on the far western prairies, 

 beyond the Missouri, in Texas, Kansas and Nebraska, is due to the fact that 

 over those regions there extends great limestone zones, destined to be the most 

 important wheat fields of the continent, which experience is demonstrating yearly, 

 as each season the "golden belt" is pushed farther westward. 



The civilization and subjection of the "Great American Plains" to the uses 

 of man, is not then a question of inherent fertility of soil, but of aridity of cli- 

 mate, and possibility of ameliorating changes through his agency, in the creation 

 of forests, and improved systems of irrigation, upon which depends the solution 

 of the question. 



The effects of forests upon climate are manifold, and in those countries from 

 which they have been ruthlessly torn by the ignorance of man we may read a 

 lesson how climate is modified by their presence, and how the vast interior area 

 of the United States, if it can be clothed with arborescent forms, will be meta- 

 morphosed into the best agricultural region of the continent. 



