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to be found in plants and animals, but not all in any one plant or 

 animal. These primaries are sometimes found in progressed con- 

 ditions and combined with each other. Thus the substances 

 known as carbonic acid and lime are found in the marble and 

 chalk. Chemists say that these are Isomeric compounds, that 

 they are alike in composition. Thus the analysis of a piece of 

 Parian marble, and of the chalk cliffs of England, will give alike, 

 as results, carbonic acid and lime, and in the same relative pro- 

 portions. Notwithstanding the apparent similarity, as shown by 

 analysis, their weight is different, nor will any amount of grind- 

 ing render the powdered marble as light as the chalk. There is 

 no treatment which can be given in common to both of these sub- 

 stances, which will render each equally valuable as food for plants. 

 Nature's laboratory seems able to create differences which escape 

 the chemist. In many of our lime-stone districts, such as Dutchess 

 and Westchester counties. New- York, the farmers find it necessary 

 to burn the lime-stone and then expose it to the atmosphere before 

 its use in the soil, until it becomes carbonate of lime, by absorb- 

 ing carbonic acid; and, notwithstanding the fact that their soil is 

 a debris of lime-stone, (at least in part) still they cannot obtain 

 full and remunerative crops until a new portion thus treated has 

 been added. If, however, they should add a thousand bushels per 

 acre of lime so prepared, the soil would cease to be fertile. Not- 

 withstanding this truth, we know that the soil of the plains of 

 Athens contains forty-two per cent of carbonate of lime, and that 

 many of the chalk soils of England contain a much larger 

 quantity. Still they are fertile. The chemist will tell us that 

 marble dust, the lime used by the Westchester farmer, the chalk 

 cliffs of England, are all of the same composition, and are Isomeric 

 compounds, and many have supposed that their effects would be 

 alike. The fact is that the English soil, and the soil of the plains 

 of Athens, with ten times the quantity of lime which would ren- 

 der another soil barren, if the lime were made from our lime- 

 stone rock, are still fertile and capable of raising full crops. Thus 

 it is clear that a difference exists, which chemistry alone cannot 

 point out. Still, when the true cause is understood, there is no 

 difficulty in comprehending its action. The plain truth is, that 

 every time one of the primary substances, originally from tho 



