224 ON THE CHEMICAL CONSTITUENTS OF SOILS. 



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 with iron . 0*505 



Sulphuric acid in combination with lime . 0*068 



Chlorine in common salt , . . 0*006 

 Humus ...... 1-109 



100*000 



This soil does not suffer from want of drainage : 

 it is well exposed to the sun, is in an elevated situa- 

 tion, and in a good state of cultivation. In order 

 to ascertain whether the rust was due to the con- 

 stituents of the soil, (phosphate of iron?) or to cer- 

 •tain 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. Upon 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 development of rust. 



13. Soil of a heath, which had been brought into 

 cultivation in the vicinity of Brunswick. The analy- 

 sis was made before any kind of crops had been 

 grown upon it. Corn-plants were first reared upon 

 the new soil, but were found to be attacked by rust, 

 even on those parts which had been manured respec- 

 tively with lime, marl, potash, wood ashes, bone-dust, 

 ashes of the heath plant, common salt, and ammonia. 

 100 parts contain: — 



Silica with coarse siliceous sand . . 51.337 



Alumina ..... 0528 

 Protoxide and peroxide of iron in combination 



with phosphoric and humic acids . . 0*398 



Protoxide and peroxide of manganese . . 005 



Lime in combination with humus , . 0230 



Magnesia idem . . . ' . . 0-040 



Potash and soda . . . . 0*010 



Phosphoric acid . . . . 0066 



Sulphuric acid .... 0*022 



Chlorine . . . . . 0*014 



Humus soluble in alkalies . . . 13-210 



