THE MATERIAL RESOURCES OF LIFE, 347 



of a continent, and then, shedding their water on the Andes, leave 

 their ammonia (it may be supposed) to find its way by some means 

 to the valleys of the western slope. 



Again, these same mountain-valleys of Peru may claim to have 

 given the world still another token of unexampled sources of nourish- 

 ment, in the growth of the cinchona-tree^ bearing the richest stock of 

 nitrogenous bases in the vegetable world. It seems, indeed, more 

 than a coincidence that this narrow, rainless, wind-nurtured slope of 

 land should send to all the earth three such eminent resources as 

 Peruvian nitre, Peruvian guano, and Peruvian bark. 



Another of the materials adequate for no more than the needs of 

 life is phosphorus. This element so far differs from nitrogen that it 

 is not found uncombined in Nature, and if separated by art it immedi- 

 ately enters into combination on exposure to the air. It occurs chiefly 

 as phosphate of lime, taken from the mineral kingdom by plants and 

 also by animals. The hard part of bone is about nine-tenths phos- 

 phate, and phosphorus is an element of molecules organized into mus- 

 cle and nerve. 



The proportion of phosphates in the crust of the earth below 

 organic remains is very slight, insufiicient for the support of the 

 higher forms of vegetable or animal life. It has been concentrated 

 and gathered into the soil by the selective agency of the organic 

 world, as it continues to be concentrated from the soil by each indi- 

 vidual plant, and from vegetable products by each individual animal. 

 Nearly all the phosphorus accessible on the planet has been a constit- 

 uent of living bodies. Its proportion in the soil is a main factor in 

 the growth of cereal grains. Ah-eady, and with the stretch of land 

 to the westward, bone-earth and phosi^hatic guanos are well known in 

 American markets. When phosphates fail at the root of the plant, 

 grain fails at the mill ; and when, from waste at the mill, phosphates 

 fail in the bread, the bones and the teeth fail in growing bodies. The 

 improvidence that leaves excretory phosphates to be washed away to 

 the salt sea, farther from the reach of life than they were in the primi- 

 tive rocks, is an improvidence that prepares an inheritance of poverty 

 for after-generations. And the ruthlessness that permits the j)urvey- 

 ors of food to sift phosphates from the food of men does its part to 

 enfeeble the present generation. 



There remains to notice another representative of the adequate 

 resources, potassium. The statements made as to the supply of phos- 

 phorus, with some reservation, become true for potassium. Certain 

 of the rocks contain a proportion of it, but from insolubility this is 

 slowly available, and is insufficient for the needs of higher organic life. 

 The soils contain more, because the organic world has gleaned for 

 the soil. Potassa and soda are two alkalies which replace each other 

 in the laboratory at theconvenience of the chemist, but, in the choos- 

 ing of the living cell, one of these is always taken and the other left. 



