AMERICAN INSTITUTE. 355 



tliat grew fruit perfectly until a belt of forest-trees that sheltered them was 

 cut down, and then the curculio attacked these trees and has since destroyed 

 all the fruit. 



Wm.S. Carpenter. — A neighbor of mine practices building fires through 

 his orchard during the month of May, which he thinks destroys a great 

 many insects. 



The Chairman said that he had tried the plan of building fires, without 

 'any benefit. 



GYPSUM. 



Mr. Pell. — The mineralogical name of which is plaster of Paris, and the 

 chemical name sulphate of lime, from the fact that it is composed of sul- 

 phuric acid and lime. Both of these important substances, particularly 

 the former, are sometimes deficient in soils, when the application of gypsum 

 is attended with a very happy effect, being found to exert an influence 

 peculiarly favorable on all leguminous plants, such as peas, clover, &c., 

 towards which it acts as a powerful invigorator, and will always be found 

 indispensable in soils deficient in lime and sulphuric acid. 



It possesses another exceedingly valuable property, that of fixing ammo- 

 niacal gases. When the carbonate of ammonia comes in contact with 

 sulphate of lime carbonate of lime and sulphate of ammonia are immedi- 

 ately formed. Sulphate of ammonia is a permanate salt; the ammonia 

 becomes fixed ; and, consequently, protected from injury by volatility. 

 Carbonate of ammonia rises from our manure heaps in large quantities ; 

 besides which, it exists naturally in the atmosphere. 



When our soils are found to contain lime, we may form gypsum in them, 

 by adding sulphate of soda, or dilute sulphuric acid. If the former is made 

 use of, it leaves the soda in a very short time, and becomes gypsum. 



This substance is a crystaline compound, and occurs as a mineral deposit 

 in various parts of the world. 



According to Kollner, the action of gypsum depends upon the power 

 possessed by lime, to form with the oxygen and carbon of the atmosphere 

 compounds, which are favorable to vegetation. According to lluckert it 

 acts like any other food ; according to Mayer it merely improves the 

 physical properties of the soil ; while, according to Riel, it is an essential 

 constituent of the plant. Hedwig called gypsum the saliva and gastric 

 juice of plants. Humbolt and Albert Thaer considered it as a stimulant, 

 by which the circulation of plants is promoted ; and Chaptal ascribed its 

 action to a supposed power of supplying water and carbonic acid to plants. 

 Davy regarded it as an essential constituent of plants, while other English 

 agriculturists have supposed it to promote fermentation in the soil. Lan- 

 bender says it acts as an exciting power, without mixing itself with the 

 sap of the plant. According to Liebig it fixes the ammonia of the atmos- 

 phere ; and if Sprengle and Braconnot are right in their surmises, it sup- 

 plies sulphur for the formation of the Icgurain of leguminous plants. 



Der Pflanzen says that gypsum consists of the oil of vitrol and quick 

 lime; and that, when it acts upon carbonate of ammonia, in a moist state, 



