hy Liindley's Theory of Horticulture. ^QS 



and is hurtful, and hence the necessity of turning dunghills, 

 especially if all composed of horse dung, and in warm situa- 

 tions ; too much cold rain checks fermentation, and hence the 

 benefit of covering from this. Before carbon can be admitted 

 into the spongioles of the roots, it must also, it is said, be made 

 soluble, by being mixed with alkalies into a saponaceous matter. 

 The alkalies necessary for this purpose are contained in the 

 manure, or may be increased by applying lime, salt, and other 

 alkaline substances. The dark brown-coloured substance in 

 well-rotted manure formerly denoted vegetable extract, but now 

 humus is formed of the proper mixture of these substances, 

 and is the essential requisite in the food of plants. It is this 

 substance which gives the colour to the drainings of the dung- 

 hill ; and, being in a soluble state, we see hence the great 

 benefits derived in watering with manured water. Dung from 

 high-fed animals is most superior. Bullock's blood is rich in 

 carbon, and should be mixed. A simple easy method of know- 

 ing the quantity of humus in soils was lately given in Paxton's 

 Magazine. Sift and wash the soil repeatedly, till all the impal- 

 pable powder it contains is separated with the water. Put this 

 into a long narrow glass vessel of water, and shake it up well 

 from the bottom : the alumina will fall to the bottom, and 

 deposit quickly, while the humus will float on the top for a con- 

 siderable time. We may thus have a pretty rough guess of the 

 quantity, both of alumina, or clay, and humus contained in the 

 soil ; and without a due proportion of the first, to retain humus 

 and moisture, no soil will be rich. The presence of animal 

 matter in the soil may be detected by the smell given off, similar 

 to burning feathers^ on burning a portion of the soil ; and the 

 presence of chalk or lime may be known by its effervescing with 

 an acid, and giving off air-bubbles and heat. For a complete 

 analysis of soils and manures, so far as at present known, as 

 useful in practice, I would refer to that lately given in the 

 Qiiarterly Journal of Agriculture, by Dr. Madden ; and, as the 

 table he gives of their actions contains so much information in a 

 little space, I have subjoined a copy of it. 



In the work before us. Dr. Lindley confines himself to a 

 statement of their general principles, and the manner in which 

 they act. He also notices the other metals and minerals, &c., 

 found in some plants, and the necessity of these in the soil to the 

 perfect growth of the plant. He also notices the best times of 

 applying manures, which, he says, are October for grass lands, 

 and spring for cultivated crops ; also the necessity of applying 

 manures to the extremities of the fibres of the root, to the 

 young spongioles, and not at the bole of the stem, which he 

 humorously likens to feeding a man through the soles of his 

 feet. 



