42 MANURES. 



the best stable manure. In respect to the quality of the grain, 

 as seven to five. In respect to the quantity, as five to four. In 

 respect to the durability of its effects on the soil, as three to 

 two. But no account is here made of the difference of the cost 

 of the two applications the lightness of transportation of the 

 bone manure, and the ease of applying it to the soil. 



Bones are less beneficial when applied to clay lands than to 

 lighter soils, and in wet seasons than in dry. Although the 

 quantity of the material employed is very small, it is not quickly 

 exhausted, but extends its influence to future seasons. For the 

 production of a single crop, an increase beyond a certain quan- 

 tity is not found to be attended with any benefit; so that a small 

 quantity is frequently seen to be applied with equal advantage 

 as a large. 



Horn is a substance of similar properties, and equally effi- 

 cient as a manure; but it is obtained in very limited quantity, 

 and its general importance is therefore greatly inferior to that 

 of bones. Yet, in large cities and towns, it is not unfrequently 

 the case that comb-makers' shavings and offal may be collected 

 in considerable quantities. 



Hair and feathers are similar in their composition to horn, 

 but, like it, are of little importance, from the limited quantity 

 in which they can be obtained. They are also slowly decom- 

 posable; and of that class of manures which may be applied to 

 trees, which require a slow and not a rapid action. 



Woollen substances are also of the same chemical composi- 

 tion as those last mentioned. They only become soluble, how- 

 ever, after a considerable time. Nevertheless woollen rags 

 form a good and lasting manure. They are to be cut into 

 small pieces, spread upon the surface of the ground and then 

 covered. They are used in the extensive hop districts of 

 England, for the manuring of that plant. 



II. MINERAL MANURES. 



ACCORDING to Professor Low, the mineral substances which 

 are employed as manures may be supposed to exert two 

 modes of action. First, they may act upon the soil by im- 

 proving its texture, or by rendering soluble the parts of it 

 which are insoluble; or by otherwise fitting it to promote the 

 growth of plants. Secondly, they may act immediately upon 

 the plant itself, by being received into its substance. 



"We cannot generally distinguish when a mineral substance 

 acts upon the plant, through the medium of a change in the soil, 



