420 
GEOLOGY OF THE FOURTH DISTRICT. 
seed ; and in less than ten weeks from the time of sowing, three tons of hay to the acre were 
cut from the meadow. The composition of this marl is admirably adapted to fertilize such 
soils, producing a mixture of calcareous, aluminous and vegetable matter. Without dwelling 
on particular localities, we may observe, that this marl may be found on almost every farm 
in the southern range of towns in this county. 
Gypsum. — Plaster. 
The gypseous rocks extend across the southern part of this county, occupying all that por¬ 
tion south of Black creek, and between it and Allen’s creek. In one or two localities gypsum 
has been found south of Allen’s creek, but the formation is soon succeeded by the corniferous 
limestone. Plaster has been obtained in small quantities at Cartersville, in the town of Pitts- 
ford, but the quantity was not sufficient for profitable working. At this place, the marl is 
decomposed to the depth of fifteen feet, and presents the appearance of a greenish grey clay. 
Marl of this character appears in several places along the canal, near this place and at Fair- 
port, but the quantity of plaster contained in it is too small for working. 
The workable beds of gypsum are almost wholly confined to the southern part of the forma¬ 
tion. Along the valley of Allen’s creek, and Mill creek, two miles farther north, most of the 
plaster of Monroe county is obtained. Both these places are in the town of Wheatland. In 
the towns of Riga and Chili, gypsum is found in thin seams, and small nodules disseminated 
throughout the rock. In these place, marls, which readily crumble on exposure to the air, 
can be substituted for gypsum. Until within a few years, the value of plaster, as a manure 
or stimulant for vegetation, has not been generally appreciated, but it is now much used; the 
demand is constantly increasing, and will doubtless continue to do so. It is mostly employed 
on grass lands, particularly on clover, as preparatory to a crop of wheat. It is also used on 
wheat crops in the fall and spring, and Indian corn is much benefitted by the use of plaster. 
One bushel to the acre is generally considered a sufficient quantity for grass crops. 
'The manner in which plaster affects vegetation, is asserted by Liebig to be by a decompo¬ 
sition, in which the sulphuric acid becomes combined with ammonia, which then acts upon the 
vegetation. This process, however, is not admitted by all to take place, and the operation of 
plaster seems yet obscure. In the use of this, as well as many other manures, the fact is 
overlooked, that plants are supported, in a great degree, by carbonic acid, and that much of 
this food is taken up by that part of the plant above ground. In this view of the case, any 
substance, above or beneath the surface, which presents carbonic acid to the plant, affords it 
food. Thus many substances which do not enter into the composition of plants, afford much 
food for them, either by absorbing this gas from other bodies and giving it to the plant, or 
affording it from their own decomposition. 
At present, about 5000 tons of plaster per annum are obtained from the town of Wheatland ; 
of this quantity, 4000 tons are used in Monroe county. This, however, is not the whole 
amount used in the county, as much plaster is brought from counties further east. Of the 
5000 tons, 1500 tons are obtained from Mr. Garbutt’s farm, in. the north part of Wheatland ; 
