12 On the Theory of Manures. 



adding a little more earth and haulm if necessary. All the, 

 urine, night-soil, soap-suds, soot, and all the domestic refuse, 

 should be carefully added to the heap ; the coal-ashes, unless 

 sifted to a small powder, being kept by themselves. Sea-weed, 

 when to be had, is an excellent ingredient in such composts ; 

 and all brush-wood, furze, &c., chopped small. All animal re- 

 mains, refuse offish, hair, wool, rags, horn, bruised bones, and 

 all refuse of the kind, should be carefully collected : animal re- 

 mains are the richest in nitrogen. To a mixture of the above 

 substances, half the bulk of manure when coarse, and about \ 

 or i when more concentrated, should, when rotted together, 

 be equal in value to the same bulk of rotted manure ; prevent- 

 ing the loss in the way manure is generally managed, and in- 

 creasing the quantity in an immense degree. When the heap 

 is near the field less dung may sufiice to mix, but when it is to 

 be carted far it should be rich, to save expense ; the heap 

 ferments more perfectly with a good proportion of hot manure. 

 For such as root-weeds and seeds of weeds, there must be a hot 

 fermentation to destroy them. When there is not much stable 

 manure to mix with the compost, a mixture of wood-ashes, lime, 

 and other substances yielding alkalies, is very beneficial, in 

 causing the production of humic acid, forming humates with 

 the alkalies in place of carbonic acid. Where much ammonia 

 is in the compost, which will be the case wherever animal remains 

 and excrements abound, lime is apt to cause the escape of am- 

 monia, by decomposing its carbonates and humates ; and only so 

 much should be used as will saturate the surplus of humic acid 

 not taken up with ammonia. Sprengel recommends about y q- for 

 some composts ; too much should, above all, be avoided. When 

 sulphate of lime, sulphate of soda, and muriate of soda (salt), 

 are cheap, they will be useful to add. The refuse of glue manu- 

 factories is rich in nitrogen. The refuse of woollen factories is 

 rich in soap-suds, urine, &c. The refuse of tanners and skin- 

 ners, the hair, skin, wool, and hoofs, is rich in nitrogen. The 

 refuse of gas-works is well known as beneficial. 



As regards the way in which carbon, forming the greatest 

 proportion of any of the elements in plants, is obtained, there 

 is still very considerable diiFerence of opinion. As we noticed 

 in former essays. Professor Liebig is of opinion that most, if 

 not all, is got by the leaves from the air ; while Professor 

 Schlieden, one of the most eminent physiologists of the day, in 

 a criticism of the Chemistry and Physiology applied to Agri- 

 culture, of Liebig, (translated into the Gardener's Chronicle,^ 

 seems to be of a completely opposite opinion. The action of 

 leaves on a growing branch confined in a vessel filled with air, 

 in which it has been said the carbonic acid has, after a time, 

 been found diminished and the oxygen accumulated, has always 



