L. V. BELL'S ADDRESS. 583 



down and broken up by friction, changes of temperature or in- 

 ternal decompositions, and the air and water which enter into 

 the composition. 



In burning out the organic part of a soil, the gases given off 

 are in fact only four, and make up all that does not remain 

 in the ashes. These gases although resembling each other in 

 some outside particulars, as transparency, compressibility and 

 freedom from color, are as widely removed from each other in 

 essential characteristics, as aqua fortis, or alcohol, or water. 

 Their character could not be determined from mere sight, as 

 seen in or rather through a clear glass jar, but let bottles con- 

 taining these four gases, be sent to a practical chemist, and he 

 could be in no more danger of confounding them, than he 

 would be in identifying milk or vinegar. 



We then have, as the entire constituents of all plants, these 

 four gases ; carbon, oxygen, nitrogen and hydrogen, and what- 

 ever may be in the ashes, which is left. 



The proportionate amount of organic matters in soils is very 

 variable. In some pure sands you cannot burn out one per 

 centum, and in some peaty soils, you may burn up seventy- 

 five per centum, three-quarters of the whole weight, after the 

 water has been all evaporated. The inorganic matters of the 

 soil, having all come from the decomposition of the surface 

 rocks, comprises of course a vast many elementary ingredients. 

 There might, in fact, be as many as there are mineral or me- 

 tallic substances known. But so far as vegetable growth or 

 the agricultural relations are concerned, it is obvious that very 

 many of the possible elements are entirely inert and unneces- 

 sary. Gold dust, for example, we have the best authority for 

 believing, exists in admixture with fertile soils in California 

 and Australia, but can do neither good nor harm to the root- 

 lets of the vegetables, opening their mouths around it. So 

 that in practical effect, many of the constituents of the soil may 

 be thrown quite out of consideration, so far as vegetables used 

 for human food are regarded. 



In fact, the fairly agricultural soils may have only about a 

 dozen of the now more than fifty elementary bodies, of which 

 we know all created things are formed. To be sure, if one 

 were to attempt to grow certain plants which are known to 

 contain rare elements, it would be necessary to look beyond 



