PEOCEEDINGS OF THE FARMERS' CLUB. 361 



pyrites was the cause of value. Prof. Rogers ascribed it to 

 potash. Professor Johnston says the one or one and a half per 

 cent, of phosphate of lime does it. 



From five to twenty loads per acre often produce quick and 

 decided effects. From 100 to 200 loads to the acre will last 

 fifteen or twenty years. 



Some parts of layers are poison and are called burning marls, 

 and will destroy vegetation for years. Some of the clays above 

 and below the marl will do this also. This is owing to sulphate 

 of iron or copperas, and, occasionally, some alum mixed. 



It is easy to detect these by well known tests and they can 

 readily be avoided. You may even taste them. 



The water taken from wells sunk in these places will turn tea 

 black if infused in it. The green sand marl when crushed on 

 paper will leave a green stain. It is said the best marls have the 

 most phosphoric acid. The counties of Monmouth, Ocean, Bur- 

 lington, Camden, Gloucester and Salem, lie in the course of this 

 sand marl. The shell marls are in Salem and Cumberland coun- 

 ties, on the Delaware, Marl is also found in Sussex county, the 

 northwest of the State and bordering on New York. 



The shell marls are found under about 20 feet of sand, but is 

 usually taken from the banks of the water courses. It is from 

 10 to 14 feet thick, and is filled with shells, mostly in a crumb- 

 ling state, and slakes to a fine powder when exposed to the air. 



ANALYSIS. 



Squankura. Burlington. 



Water ^ 10.600 10.410 



Silica 51.162 • 55.930 



Protoxide iron 16.200 ) oo qkk 



Alum 6.100^ "^"^-^^^ 



Potash and soda _ 4.274 5.800 



Lime 3.478 1.640 



Magnesia ._ 2.037 1.013 



Phosphoric acid 4.540 1.680 



Sulphur 0.429 0.957 



100. 100. 



A bushel when dry weighs about 80 pounds, 4 pounds of which 

 is potash, or nearly as much as there is in a bushel of unleached 

 wood ashes. The two per cent of phosphoric acid (and often 



