S2' An Account of the JVliitten Plastef^ 



the vitriolic acid. But as its fertilizing effects are tlie 

 same, or nearly so, it goes far to demonstrate the cor- 

 rectness of an opinion I have long entertained, that the 

 vitriolic acid, by some considered hostile to vegetation,, 

 is in truth the only operative ingredient in gypsum. This- 

 acid, chemists inform us, will attract six times its vi^eight 

 of vi^ater from the atmosphere, before it will be satura- 

 ted. Now the Plaster of Paris, which is said to contain 

 thirty parts in one hundred, of this acid, produces no 

 effect but on sandy or gravelly soils. It should seem, 

 that as fast as the acid attracts the moisture, the thirsty 

 soil receives it, and in this way the plaster becomes a 

 faithful and excellent conductor of humidity to the plant. 

 Whatever may be the cause, it is certain that a small 

 quantity of pulverized gypsum, exposed upon a dry stone 

 to the open air, in a warm and clear day, will presently 

 by the attraction of water from the air, become a mere 

 paste. It is difficult to account for its astonisliing effects 

 upon vegetation in many parts of our country, on any 

 other hypothesis. 



My principal object in making this communication, is, 

 to obtain a more perfect analysis of this newly discover- 

 ed manure, in hopes it may be employed to advantage 

 iipon the sea- coast, where,, I am informed, gypsum pro- 

 duces no visible effect. 



The paper No. 2, contains stones of a singular form 

 and appearance, sent me by a gentleman in Winchester, 

 to be communicated. He informs me they are found in 

 considerable quantities in that town, sometimes in large 

 masses, which, when struck with a sledge, will fly into 

 pieces of different sizes, retaining uniformly the hexag- 

 onal figure. From their assuming universally the form 

 of hexagonal prisms, and from their transparency and 

 hardness, I conclude they must be, if not the rock crys- 

 tal^ at least a very pure species of silex. But of what- 

 ever substance they are composed, it is possible in the 

 hands of a skilful lapidary, the}^ may be turned to a good 

 account. I am. Sir, respectfully. 



Your obedient servant, 



JOHN C. SMITH. 



S. Baldwin, Esq. Rec. Sec. Ac. Ar. Sci, 



