FLORENCE MARBLE. 115 
of shells, whence it frequently has the name of shell 
marl ; and where these are predominant, it affords an 
excellent manure for sandy, dry, gravelly, or light 
lands. Marl likewise produces very beneficial effects 
on mossy and clayey soils ; and these effects, where it 
has been properly applied, have been observable for 
twelve or fourteen years. Some kinds of marl that con- 
tain but a small portion of lime have been successfully 
used in the manufacture of earthen-ware. 
This mineral is usually found at the depth of from 
five to nine feet beneath the surface of the ground, and 
deposited between beds of clay and sand. It is dug out 
with spades ; and, in the digging of it, in Ireland, the 
workmen not unfrequently meet with the horns of deer 
and other curious fossils. 
The usual mode by which persons, generally unac- 
quainted with minerals, distinguish this from other clayey 
substances, is, to break a small piece of dry marl into a 
glass of vinegar. If it be marl it will immediately dissolve 
with considerable effervescence ; and the briskness of 
the effervescence will be in proportion to the quantity 
of lime which it contains. 
189. FLORENCE MARBLE is a kind of indurated or 
hardened marl, and is remarkable for presenting, zohen po- 
lished, the appearance of ruined edifices or rocks. 
This kind of marble is never used in architecture. 
Little slabs of it are cut for Mosaic work, and to be 
framed like pictures ; and the latter, when of consider- 
able dimensions, are sometimes purchased at a high 
price. If held at a distance from the eye, an inexpe- 
rienced observer might mistake a slab of Florence 
marble for a drawing in bistre. Here, observes a 
French writer, we remark a shattered Gothic castle, 
there the mouldering fragments of a cathedral ; in one 
part ruined walls, and in another shattered bastions and 
towers. But, when we approach the picture, the illu- 
sion vanishes, and those imaginary figures which, at a 
distance, appeared to be so correctly drawn, become 
