PLASTEE OF PARIS. 371 



benefit natural pastures. This, I apprehend, depends 

 chiefly on the character of the soil. In one instance, 

 within my knowledge, a -large pasture, which had be- 

 come worn and somewhat unproductive, received a 

 generous top-dressing of plaster. The grass started 

 sooner, and continued throughout the season to look 

 far better, than the adjoining pastures of precisely the 

 same soil. So far as could be ascertained, the increase 

 in grass over the adjoining pastures was about seventy- 

 five per cent. Nor was this all. This pasture came in 

 the next season with the greatest luxuriance, and its 

 load of beautiful green was the wonder of the neighbor- 

 hood. Its effect on clover and Timothy is even greater 

 than on old pastures. Many have supposed that plaster 

 would exhaust the soil. That this could not be the 

 case will appear from the fact that it takes four hundred 

 and thirty parts of water to decompose one part of 

 plaster, while its decomposition is so slow that its influ- 

 ence is felt for several years. How, then, can it have 

 such immediate and beneficial effects ? It is generally 

 explained by saying that it retains the fertilizing gas, 

 which is constantly rising from fermenting vegetable 

 matter, and gives it up, at a proper time, for the nourish- 

 ment of the plant. It does not, like lime, cause vege- 

 table matters to decay, but rather, when they decay, 

 holds their most important parts from escaping. 



The infectious odor which rises from decaying vege- 

 table matter, from the stable, from the manure heap, and 

 imperceptibly from the whole surface of the earth, is 

 one of the most important elements for the growth of 

 the plant. Plaster fixes this, and the first shower 

 washes it into the earth to feed the roots of plants. 

 The relative value of manure depends, in a measure, 

 according to the generally received opinion on this 

 subject, upon the amount of this noxious odor, or the 



