SECT. V. EARTHS. 7f 



analysis of Klaproth ; and in that state of division 

 in which it is precipitated from its solution in fixed 

 alkalies, it is perfectly soluble in 1000 parts of 

 water.* Magnesia is soluble in water by means of 

 the mineral acids, and even in pure water, in very 

 small quantities ; requiring about 2000 times its 

 weight to hold it in solution. 



All the earths, then, found in plants are less or 

 more soluble in water. And if it be said that the 

 proportion in which they are soluble is so very small 

 that it scarcely deserves to be taken into the account, 

 it is to be recollected that the quantity of water 

 absorbed by the plant is great, while that of the 

 earth necessary to its health is but little, so that it 

 may easily be acquired in the progress of vegetation. 



Such is the manner in which their absorption 

 seems practicable : but the following experiments 

 afford a presumption that they are actually absorbed 

 by the root. Woodward took three plants of Spear- 

 mint, one of which he made to vegetate in distilled 

 or pure water ; another in river water ; and a third, in 

 water mixed with mould. At the commencement 

 of the experiment the first plant weighed 114 

 grains ; at the end of the experiment it weighed 

 155 grains, being augmented by 41 grains. The 

 water expended was 8863 grains, and the increase 

 as 1-214 +. At the commencement of the ex- 

 periment, the second plant weighed 18 grains, at 

 the end 54 grains, being augmented by 26 grains. 



* Kivwan's Miner, vol. 5. p. 10. 



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