332 



THE IRRIGATION AGE. 



water trickles through the soil it surrenders the oxygen 

 to the plants with which it comes in contact, and min- 

 isters to their growth and nourishment in various ways 

 to be hereafter explained. 



But the quantitiy of oxygen stored in solid rocks 

 is still more remarkable. Nearly one-half of the rocks 

 which compose the crust of the earth, of every solid sub- 

 stance we see around us, of the soils which are daily 

 cultivated, and much more than one-half of the weight 

 of living plants and animals, consist of this elementary 

 body, oxygen, known to us only as an invisible, im- 

 ponderable, unperceivable gas. 



HYDROGEN. 



Hydrogen is also known to us in the stale of gas, 

 and like oxygen is without color, taste, or smell. It is 

 unknown in a free or simple state, although chemists 

 have succeeded in obtaining it in small quantities, and 

 is not so abundant as either carbon or oxygen. It forms a 

 small percentage of the weight of animal and vegetable 

 substances, and constitutes only one-ninth of the weight 

 of water. With the exception of coal and mineral oils 

 known as "hydro-carbons," it is not a constituent of 

 any of the large mineral masses of the globe. 



It does not support life, and animals and plants 

 introduced into it speedily die. It is the lightest of 

 all known substances, being fourteen and one-half times 

 lighter than air. Water absorbs it in very small quan- 

 tities, one hundred gallons of water taking up no more 

 than one and one-half gallons of it. 



NITROGEN. 



This substance is likewise known only in a state 

 of gas. It exists in the atmosphere in the proportion 

 of seventy-nine per centum of its entire bulk, and 

 is without color, taste, or smell. It is lighter than 

 atmospheric air in the proportion of ninety-seven and 

 one-half to one hundred, and is deadly in its pure state 

 to both animals and plants. It is essential in the at- 

 mosphere we breathe, moderating the combustion which 

 would ensue if the air were pure oxygen, and forms a 

 part of many animal and some vegetable substances, 

 but does not enter, except in small proportions, into 

 mineral masses. It is less abundant than any of the 

 so-called organic elements, but it performs certain 

 most important functions in reference to the growth 

 of plants. Spring and rain water absorb it as they 

 do oxygen, from the atmosphere, and bear it in solu- 

 tion to the roots of plants, one hundred parts of water 



HON. JOHN HENRY SMITH. SALT LAKE CITY. 



dissolving about one and one-half to four per centum 

 of the gas. 



PROPORTIONS OF THE FOREGOING ELEMENTS IN PLANTS. 



Although the substances of plants are composed 1 

 mainly of the above organic elements, they exist in 

 very different proportions. This will appear from the 

 following table of "dried" plants, taking one thousand 

 parts by weight as the standard : 



Clover Grass, Pota- 



Oats. seed. hay. Peas. Wheat, toes. 



Carbon 507 



Hydrogen ... 64 



Oxygen 367 



Nitrogen .... 22 

 Ash 40 



T. C. NYE, LAREDO, TEXAS. 



1,000 1,000 i;ooo 1,000 1,000 1,000 



The above proportions are slightly variable, but 

 the figures given represent nearly the relative weights 

 in which these elementary elements enter into forms 

 of vegetable matter. Herbaceous plants generally leave 

 more ash. that is, inorganic matter, the wood of trees 

 and the different parts of plants yielding unequal quan- 

 tities. 



HOW ORGANIC ELEMENTS COMBINE TO FORM PLANT? 

 FOODS. 



Carbon being a solid, and insoluble in water, can 

 not be taken up through the pores of the roots of 

 plants, the only parts with which it can come in con-- 



