0 
ELEMENTS OF AGRICULTURE. 
United States, particularly along the seaboard, and m the 
southwestern states, where it abounds in vast beds of the 
finest quality. In New Jersey, Delaware, Maryland, and 
Virginia, exhausted and wornout lands have been brought 
to the highest state of productiveness by abundant marling. 
Its great abundance and richness, in the now wornout 
lands along the tidewater of the old southern states, will 
yet make them rival the virgin fertility of the western 
states, and perhaps give the tide of emigration a new di¬ 
rection. Like lime, it improves alike the texture of sandy 
and stiff lands, and it has the advantage of lime in being 
generally cheaper. 
34. Before using marl as an ameliorator, we should 
know how to discover whether a soil contains carbonate 
of lime ; and we should be able also to determine the 
quantity of this substance. To make this experiment (and 
there is no sort of difficulty about it), a portion of the soil 
to be tried is taken at a certain depth, and not on the im¬ 
mediate surface; for this last might, independent of its 
primitive composition, contain calcareous substances, 
placed there at some period more or less remote. 
35. The following is the very simple process by which 
the proportion of calcareous matter contained in marl is 
determined. Take a set of delicate scales, and after dry¬ 
ing, without hardening, one hundred grains of the earth 
to be tried, they are put in a vessel, and a sufficiency of 
water to crumble it to an earthy consistence is added. 
Upon this a few drops of nitric acid are thrown, and the 
mixture is worked up with a wooden spatula; efferves¬ 
cence immediately takes place; and the carbonic acid es¬ 
capes. This last is replaced by the nitric acid, which then 
forms a nitrate of lime. As this body has the property 
of remaining suspended in w^|er, it is expelled by several 
successive washings; taking always great care that the 
other earthy particles are precipitated to the bottom of the 
