MARL. — GREEN SAND, 
343 
itself to the philanthropic of all our large cities, 
viz;, the introduction of peat as a fuel to supply the 
necessities of the poor. It is believed that much 
suffering may be prevented and much comfort pro- 
moted, by the use of peat in all places where fuel 
is expensive, as in Nev^-York and Albany." 
Marl. — There are two substances which go un- 
der the name of marl in this country, viz. : 1. The 
Calcareous Marl, composed chiefly of carbonate of 
lime. 2. The Green Sand Marl, which we have de- 
scribed in a former chapter. 
The first kind of marl may be either a friable 
mixture of lirne and clay, or partially decomposed 
beds of shells. In the New-England States, espe- 
cially in the western part of Massachusetts, this 
marl often occurs in beds of from two to twelve 
feet thick, generally in marshes or on the borders 
of ponds. It seems to result from the carbonate of 
lime brought into ponds by water, and there depos- 
ited. After a while perhaps the pond fills up, ve- 
getables begin to grow over the marl, and thus at 
length a deposite of peaty matter covers the marl. 
When dry, this substance is nearly as white as 
chalk, and much lighter than common soil ; when 
wet, it is of a light gray colour, especially if it con- 
tains much organic and earthy matter; the quantity 
of lime it contains may generally be told by its de* 
gree of whiteness. Prof. Hitchcock states that 
this marl is found almost exclusively in swampy 
ground, generally quite wet swamps, and always 
covered by a stratum, often several feet thick, of 
black vegetable matter approaching to peat. Hence, 
as these swamps are not easily excavated, the marl 
is not apt to be discovered. Prof. H. recommends 
passing down an iron rod several feet long, with a 
groove in the end like an auger, in order to discover 
marl in places where it is suspected; or even a 
rough pole, which he says answers the purpose just 
as well, some of the substance always adhering to 
