HINDRANCES AND HELPS 



chemist, exploded the idea prevalent in his day 

 — that gypsum was beneficial by promoting 

 putrefaction of manurial substances — and ex- 

 pressed the opinion that it was absorbed by the 

 plants bodily; at least by those plants whose 

 ash showed large percentage of sulphate of 

 lime. Sir Humphry was honest; the theory 

 was not too absurd; the farmers were doubt- 

 less glad to get a handle to their talk about 

 plaster; and so for a dozen years or more, the 

 lucerne and clover went on absorbing the gyp- 

 sum. At last some inquisitive party ascer- 

 tained, by careful experiment, that a field of 

 clover not treated with gypsum contained as 

 large a percentage of sulphate of lime in its 

 ash, as another field which had been treated to 

 the salt. The inference was plain, that the 

 superior vigor of the last was not attributable 

 to simple absorption of the sulphate, and the 

 theory of Davy quietly lapsed. 



Chaptal, the French chemist, speaks of gyp- 

 sum in a loose way as a stimulator ; but in what . 

 particular direction its stimulating qualities are 

 supposed to work, he does not inform us. 



About the year 1840, I think, Dr. Dana, of 

 Lowell, published a bouncing little book called 

 a Muck Manual, in which he affirmed very 

 stoutly that gypsum was quietly decomposed 



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