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phoric acid. Whether this combination takes place before its entrance 

 into the plant, or afterward, is not a settled point. It appears, that it is 

 • essential in the formation of the grain of our cereals — corn, Avheat, rye, 

 <&c. — as in them it is found in much greater abundance, than in other 

 parts. " It is an element of food, and not of mechanical support." 



When it exists in great abundance in the soil, it is injurious to crops. 

 Although most of the lime rock of Wisconsin is a magnesian limestone, 

 yet the magnesia is so much moi'e insoluble in water, than lime, that but 

 «, small amount exists in the soil, in a condition to be taken up by plants. 



J*0TAsn. — This substance is well knoAvn to farmers generally, as the 

 material which is obtained from boiling down the ley of wood-ashes, to 

 dryness, and when it is purified and combined with carbonic acid, forms 

 the common pearl ashes of the shops. It is found in greater or less 

 abundance in plants, and is also a constituent of animal matter. Its 

 office in the plant, is not quite evident. Much is yet to be learned in 

 ■regard to it. That it is essential, however, is inferred from the fact, that 

 ^Soils destitute of it, are nearly barren. It is of great importance as a 

 '■constituent of soil, in rendering (as we have before hinted under silex) 

 isilica, and other bodies, soluble, so that it can be taken up by plants. 



Soda. — Nearly the same may be said of soda as has been said of potash ; 

 in fact, the two are much alike in many of their properties, and also in the 

 purposes which they seem to serve in plants and in soil. Some plants 

 3'equire more of soda than of potash, while others require more of pot- 

 ash than of soda. The tubers of potatoes, require both potash and 

 soda. It is thought by some that potash and soda may replace each 

 other, in case of an absence of the other in the soil. It is found, however, 

 "\vhenever this does take place, that it is a forced condition of the plant, 

 and the probability is, that in such cases the plant would in a few years 

 become so deteriorated or "run out," that it would cease to vesfetate. 



Of the last two substances there are several compounds of great 

 'importance to the agriculturist. Many of them are capable of being 

 -used as valuable manures. Of these, however, though they may often 

 -exist in the soil, and enrich it by their presence, yet we have not room 

 •or leisure to speak further. 



Chlorine. — This is a greenish-yellow colored gas or air, and has a 

 Tery pungent, disagreeable smell. Animals cannot breathe it without 

 ^suffocation ; and when mixed with common air, it speedily kills all living 



