(9 5) 
lime under the same receiver, the plant will perish; 
because the lime will take from the atmospheric air 
all the carbonic acid it contains, and thus starve the 
plant. Vegetables, placed near heaps of lime in 
the open air, suffer from the same cause and in the 
same way; but though lime, in large quantities, 
destroys. vegetation, in small quantities it renders 
vegetation more vigorous. Its action is of two 
kinds—mechanical and chemical ; the first is a mere 
division of the soil by an interposition between its 
parts; the second, the faculty of rendering soluble 
vegetable matter, and reducing it to the condition 
of terreau. | | 
The mechanical agency ascribed to lime, belongs 
also to marle and to ashes, and in an equal degree 
—but their chemical operation, though similar, is 
less. (1) 
Gypsum is composed of lime and sulphuric acid. 
Mayer was the first to present to the publica series 
of experiments upon it, in its relation to agriculture. 
Many chemists have followed him, and a great varie- 
ty of opinion yet exists with regard to its mode of 
operation. Yvart thinks, that the action of gypsum 
is exclusively the effect of the sulphuric acid, which 
enters into its composition; and founds this opinion 
upon the fact, that the ashes of turf, which contain 
sulphate of iron, and sulphate of alumina, have the 
same action upon vegetation as gypsuin. Laysterie, 
observing that plants, whose roots were nearest the 
surface of the soil, were most acted upon by plaster, 
(1) Vegetable ashes are lime, combined with an earthy saline matter. 
