ANALYSIS OF SOILS. 231 



Even the grain is covered with a yellow rust, and is much 

 shrunk. One hundred parts of the soil contain 



&quot; Silica and fine silicious sand, 87.859 



Alumina, 2.652 



Peroxide of iron, with a large proportion of prot 

 oxide 5.132 



Protoxide and peroxide of manganese. .... 0.840 



Lime, principally combined with silica, .... 1.459 



Magnesia, idem, 0.280 



Potash and soda, idem, 0.090 



Phosphoric acid in combination Avith iron, . . . 0.505 



Sulphuric acid in combination with lime, . . . 0.068 



Chlorine in common salt, 0.006 



Humus, 1.109 



100.000.&quot; 



This analysis must surely be sufficiently close and severe to 

 satisfy even the most fastidious ; for here even six hundred 

 thousandth parts of a particular ingredient in the soil, that is, of 

 chlorine in common salt, were ascertained. 



&quot; This soil,&quot; it is remarked, &quot; does not suffer from want of drain 

 age ; it is well exposed to the sun ; it is in an elevated situation, 

 and in a good state of cultivation. In order to ascertain whether 

 the rust was due to the constituents of the soil, (phosphate of 

 iron?) or to certain fortuitous circumstances unconnected with 

 their operation, a portion of the land was removed to another 

 locality, and made into an artificial soil of fifteen inches in 

 depth. Then this barley and wheat were sown ; but it was 

 found, as in the former case, that the plants were attacked by 

 rust, whilst barley growing on the land surrounding this soil 

 was not at all affected by the disease. From this experiment it 

 follows that certain constituents in the soil favor the develop 

 ment of rust.&quot; 



But this inference does not appear to me to follow of course. 

 We cannot deny that the rust may have been, in this case, the 

 result of some noxious ingredients in the soil ; this appears 

 highly probable. But rust is often the result of influences 

 mainly atmospheric. The fact that the barley grown on soil in 

 the neighborhood of the removed soil was unaffected by rust, 



