31 
determined. Thus, a specimen of marl from near Marlborough, Maryland, fur- 
nished by washing— 
Dark greensand grains ......--- Ae aCe ee ee et ee 4579 
Shelly particles and clay .-..-..-.-s5---------0------. 54.21 
100.00 
Now many agriculturists would consider this marl rich in possessing the lime 
element so abundant, whereas its real value is in the amount of greensand, 
which, in the proportion above, would yield between five and six per cent. of 
potash, estimated in an uncombined form; five per cent. of this form of potash 
would represent eight and one-third per cent. of pure carbonate potash, so that 
the above amount of greensand grains would yield in 45.7 pounds about five 
pounds of pure carbonate, or just 100 pounds of the same pure salt to the ton 
of marl as now constituted. As the shelly particles were found to yield forty- 
five per cent. of carbonate of lime, each ton would yield nearly 900 pounds of 
mild lime. The analysis would thus show that the valuable ingredients in one 
ton of this marl are 100 pounds of pure carbonate potash and 900 pounds of car- 
bonate of lime. 
In a ton of farm mauure (cow) there are obtainable not quite three pounds of 
carbonate of potash, so that the amount of alkali afforded by this marl is greatly 
superior to that given by cow manure; and as an average crop of potatoes 
raised on one acre removes from the soil about 102 pounds of carbonate of potash, 
there is in one ton of this marl nearly a sufficient amount of that salt to replace 
what the potato removed, supposing the manure to be evenly spread over the 
whole surface of the ground. 
In the lower counties of Maryland the marl beds extend and cross the Poto- 
mac into Virginia, near Aquia creek, along which into the interior it may be 
traced in Stafford county. ‘The following is the constitution of a marl from the 
Maryland side of the river at that point. By elutriation, or washing, in 100 parts 
of dry matter: 
Pine -yelluweehiy .j Pej Posie Se 8 S28 Serie rie a 48.00 
Dalearedus matter, (ANeUn Gs tie.s foe See tee Se ia 18.00 
BaPRT TL Doreen) hate eae aN cde 3 3 aisle so aielalel de < aikido 10.00 
Grcendand marly dmpuarercciw ies nae Si Soe ee 24.00 
100.00 
And by chemical analysis it yielded in 100 parts: 
Quartz and fine sand ..... 3 EOE Pee ye 58.5 
Mluminaiand Perot GEMM) shee. nha nwrere's weve ts eite BY 2 
Porbandar ime pemre dl bese ts ct oS ee PN ie 
Carbonate of magnesia, traces. 
Soluble saline matter containing ? of one per cent. of potash. . 0.3 
Motstereranablepsy siacs ate. 5. oi WS ae Se 11.8 
100.0 
The proportion of potash in one ton of this marl is about twenty pounds of 
pure carbonate, corresponding to about twelve per cent. of pure glauconite in 
the marl. The carbonate of lime being seventeen per cent., the total quantity 
per ton of these two elements would be 20 pounds of pure carbonate of potash 
and 170 pounds of carbonate of lime. This marl, therefore, has one-fifth the 
money value of the one from near Marlborough. me 
