, 88 [Senate 



Marls, which exert so powerful an influence on many soils, derive 

 most of their value from the lime they contain; and with few excep- 

 tions, their power as fertilizers may be measured by the per 

 cent of lime shown on analysis. There are some marls, how- 

 ever, which are an exception to this rule; their value appearing to 

 depend on other matters than mere lime. Of this kind is the cele- 

 brated green sand marl of New-Jersey, and some other points of the 

 Atlantic coast. In this formation, which acts so powerfully as a ma- 

 nure, there is from 6 to 10 per cent of potash; an agent, which, on 

 light soils, is scarcely equaled as a manure. In addition to the lime 

 which marl contains, the influence of the proportions of sand and clay, 

 of which the balance usually consists, must be taken into considera- 

 tion in determining the value of this substance for particular soils.. 

 Thus, on heavy or clay lands, marls abounding in sand will be found 

 preferable to those the base of which is clay; and on light or sandy 

 soils, the latter will be much the most useful, the per cent of lime in 

 both cases being alike. Marl should be spread over the surface, and 

 pulverized by the action of air and frost before it is plowed under. 

 When so treated, experience proves it is a most valuable manure, and 

 a single dressing exerts an influence for many years. 



Of another salt of lime, the phosphate, notice has been taken when 

 treating of bones as a manure. It will not be amiss, however, to 

 Ph s hate ^^^^® here, that when any substance is invariably found in 

 of Lime, ^iuj part of a plant or plants, it is right to infer that the per- 

 fection of that part of the plant is impossible, unless the substance re- 

 quired is within reach of the plant while growing. Thus the stems of 

 the grasses abound in silex; some of them, the cane for instance, to such 

 a degree as to strike fire with steel, and unless this substance, in the 

 form of silicates, was presented to the plants, they would not be per- 

 fect. So it is right to infer that unless soils contain the phosphates, 

 or a supply is furnished for the use of plants, that the cereal grains 

 could never be perfected, as the seeds of these invariably contain 

 large quantities of the phosphates. Phosphates are found more or 

 less in all soils, and w^hen these are deficient, bones form an abundant 

 and accessible source for their supply. It is also found in considera- 

 ble quantities in all animal and farm yard manures, particularly in the 

 liquid part. 



Gypsum is the third principal salt of lime which exerts a powerful 

 influence on plants, and is one of the most valuable of all our mine- 



