COMMUNICATIONS. 96 



bj occasioned, became distinctly visible to passers-by, in the sig- 

 nificant words " This has been- Plastered !" It is needless to 

 say the demonstration was convincing ; so that ever since, there 

 has been no question of its valite as a fertilizer. 



But the questions of the modus operand^ of the plants to which 

 it is ajipropriate, and of the best methods of application, were 

 not so easily decided ; indeed they are not fully settled even yet, 

 notwithstanding the carefully instituted and oft-repeated experi- 

 ments of a Davy, a Liebig, and the whole world of chemists. 

 In the natural state 100 parts consist of 



Lime, 33 



Sulphuric Acid, ...... 46 



>' ater, . . . . . • . ^X 



The water contained is what chemists call water of constitution^ 

 — that is, it is essential to its character as gypsum, and exists in 

 chemical combination with it ; not so strong, however, but that 

 a heat of 300°, Fahrenheit, will expel it, leaving the mineral in 

 a finely pulverized condition, resembling quick lime. After 

 the expulsion of water of crystallization it consists of lime 41 

 1-2 per cent., and sulphuric acid 58 1-2. One ton equals about 

 25 bushels by measure. 



With iis physical properties most persons are sufficiently 

 familiar ; as also with its use as water-lime or hydraulic cement, 

 and in the manufacture of busts, statuettes, medallions, stucco 

 mouldings and other ornamental work. Unmixed with other 

 minerals it is quite white, and in some instances is crystalline 

 and translucent — when it takes the name of alabaster, and is 

 ranked among the precious minerals. 



Assuming then, what it were lost time and labor to stop to 

 prove, let us enquire into the philosophy of its action. 



In the first place, the elements of which it consists are invariable 

 constituents of all plants, and hence must of necessity become a 

 part of the food on which they subsist. And inasmuch as the 

 system of cropping involves the inevitable exhaustion, in course 

 of time, of these elements as found natively in the soil, some 

 method must be employed for restoring them, else the crop will 

 gradually dwindle 'until nothing can be produced at all ; and 



