EUCALYPTUS TBEES. 93 



being especially needed in the soil for all kinds of root- 

 crops, for vine and maize ; nor can most other plants 

 live without it altogether, although the quantity re- 

 quired may be small ; but I must add, for manuring, 

 potash by itself would be far too valuable. 



Almost every kind of forage affords potash salts, 

 these being among the necessaries for the support of 

 herbivorous animals. Their undue diminution in food 

 is the cause of various diseases, both in the animal 

 and vegetable world ; or predisposes, by abnormal 

 chemic components of the organisms, to disease. 



The muscles of the human structure require a com- 

 paratively large proportion of carbonate of potassa ; it 

 is also absolutely required in blood, predominating in 

 the red corpuscles. Plants grown in soil of rocks con- 

 taining much feldspar — such as granite, gneiss, syen- 

 ite, some porphyries, diorite — are always particularly 

 productive in potash, potassium entering largely into 

 felspatic compounds. The latter mineral yields, in 

 most cases, from twelve to fourteen per cent, of po- 

 tassa, which, if changed to carbonate, would become 

 augmented by nearly one half more. It is fixed chiefly 

 to silicic ac\ji in feldspar, and thus only tardily set free 

 through disintegration, partly by the chemic action 

 of air, water, and various salts, partly through the 

 mechanic force of vegetation.* The importation of 

 potash into Victoria during 1870 was only one hun- 

 dred and seventy tons, but, with the increase of 

 chemic factories, we shall require much more. 



It has justly been argued that the chemic analysis 

 affords a very unsafe guidance to the artisan, as re- 

 gards the quantity of potash obtainable from any kind 



* The proverb of cliejiiiatry — " Corpora non agwni, nisi Jlvifict " t- }P hepg 

 ^Jso applicabje, '" ' ' 



