40 AMERICAN AGRICULTURE. 



GREEN SAND MARL. 



There are extensive beds of a green sand (generally 

 though improperly termed) marl, which run through a section 

 of New-Jersey, from which farmers have derived an aston- 

 ishing addition to their crops. It is found by analysis to 

 contain but a small quantity of lime, but it readily yields a 

 large amount of potash, varying from 6 to 15 per cent. 

 From a careful analysis of eight different specimens, Prof. 

 Rodgers found in it an average of 10 per cent, of potassa. 

 The effect of this applied to the barren sands which abound 

 in that neighborhood, has been so favorable, that lands which 

 before could be bought for $3 per acre, would afterwards 

 bring $40. Several deposits of green sand in the counties 

 of Plymouth and Barnstable, Mass., similar in external 

 appearance to the foregoing, were explored by Prof. Hitch- 

 cock, and specimens were analyzed by Dr. Dana, without 

 however, detecting any qualities of decided advantage to 

 agriculture. 



GYPSUM PLASTER OF PARIS OR SULPHATE OF LIME. 



This is a combination of lime with sulphuric acid and 

 water in the proportion of 28 of lime, 40 of acid, and 18 of 

 water. It is frequently found in connexion with carbonate 

 of lime, clay &c. The use of gypsum has been attended 

 with great benefit in most parts of the United States ; and 

 by many of the most experienced farmers, is justly consid- 

 ered as indispensable to good farming. Like all saline, and 

 indeed all other manures, it acts beneficially only on soils 

 which are free from standing water, or which may be satu- 

 rated with it. It is felt most on sandy, loamy, and generally 

 on clay soils, requiring more for the latter, and for all such 

 as contain a large proportion of vegetable matter. From 

 two pecks on sandy, to fifteen bushels on clay soil have 

 been applied per acre; but from two to four bushels is the 

 usual quantity. 



The crops on which it produces the greatest effect are the 

 red and white clover, lucern and sainfoin, and the legumi- ^ 

 nous plants, peas, beans, &c. On natural meadows and 

 tin- cereal grains, it has no perceptible influence. 



It should be sown broadcast as soon as the leaves have 

 expanded in the spring. It takes 460 times its weight of 

 water to dissolve it, which shows the necessity of applying it 

 while the early rains are abundant, and the increased effect > 



