Oil Liquid Manure. 545 



ffxent advantage, since the porous nature of sand allows the roots 

 of plants to penetrate the soil to a great depth, and in every direc- 

 tion, in search of food. In other words, sandy soils are excellent 

 vehicles for holding a diluted liquid manure, in which the 

 different constituents occur in an immediately available, or, so 

 to say, cooked condition. 



The porous and often uniform physical character of such soils, 

 moreover, causes gi'cat fluctuations in the amount of moisture, 

 and in dry and warm weather they dry to a considerable depth, 

 leaving a porous and friable surface exposed to the action of 

 the atmosphere. 



All these are peculiarities that strikingly characterise porous 

 sandy soils, and render intelligible the improvement which liquid 

 manure is well known to produce on them. 



Let us contrast with these chemical and physical properties 

 of sandy soils some peculiarities that are most distinctly observed 

 in stiff clay land. 



III. Ox THE Characters of Soils xot benefited by Liquid 

 Manure, and on the Causes of Failure. 



Soils containing a fair proportion of clay, especially stiff clay 

 soils, are diametrically opposed in their chemical and physical cha- 

 racters to those which are porous and sandy. Generally the more 

 retentive and stiff soils contain not only the more common mineral 

 elements which we find in the ashes of plants, such as lime, 

 magnesia, soluble silica, sulphuric acid, &c., in sufiHcient abun- 

 dance, but also the more valuable mineral substances, such as 

 phosphoric acid and potash. Tliey moreover possess in a high 

 degree the power of absorbing ammonia from the atmosphere, and 

 retaining it ; and in addition to this ammonia, under good 

 cultivation, tlie vegetable remains left in such soils in the shape 

 of roots and leaves from former crops, yield plenty of organic 

 food for plants. It is true that stiff soils are not always very pro- 

 ductive, but generally speaking thoy contain within themselves 

 all the elements of fertility, and it is only for want of proper 

 cultivation that their productive powers are not fully developed. 



Whatever the agriculturist may think of the Lois Weedon 

 system of culture, the Rev. Mr. JSmith certainly has the great 

 merit of having shown with indefatigable perseverance and zeal 

 that certain clay soils only require constant working in order to yield 

 remunerative crops of wheat in succession for a number of years. 

 This would be an utter impossibility if they did not contain 

 a practically inexhaustible store of mineral elements of nutrition, 

 and if they did not under his system of cultivation also provide 

 an ample supply of organic food. 



In illustration of tliis part of my subject, I may mention the 



