ON THE IMPROVEMENT OF SOIL. 169 



the streets, dust from the roads, or earth of different de- 

 scriptions, the whole forming a rich compost. Mud from 

 the beds of rivers, when it can be obtained, is a very val- 

 uable ingredient for such a compound, as it abounds with 

 organic remains of fish, shells, reptiles, and rotten plants. 

 Often, however, before being laid upon land, it requires 

 being well turned up and exposed to the air for some time. 



Caroline. It is to be regretted that such precious rel- 

 ics should, in general, be lost by being carried by the 

 current of the river into the sea ; but the slime of ponds 

 and all stagnant waters must make very rich manure. 



Mrs. B. Yes ; they may be considered as storehouses 

 of materials, ready to return into the vegetable system. 



The elevation of temperature produced by the comple- 

 tion of fermentation of the manure, after it is mixed with 

 the soil, is but inconsiderable, excepting in garden cul- 

 ture, where, accumulated in hotbeds, it often produces a 

 temperature equal to that kept up in a hothouse. 



Short manure, that is to say, that which is thoroughly 

 decomposed, and in which the water and other evapora- 

 ble parts have in a great measure disappeared, contains 

 a considerable quantity of carbon. 



Long manure, in which state fermentation is but little 

 advanced, contains a greater proportion of water : the first 

 is, therefore, best adapted to moist, the latter to dry, soils. 



Emily. But if the fermentation be completed previous 

 to mixing the manure with the soil, are there not many 

 volatile products which escape into the atmosphere, and 

 which might, if buried in the earth, have promoted veg- 

 etation ? 



Mrs. B. JNTo doubt. It is incalculable how many val- 

 uable materials are "wasted on the desert air" which 

 should have given vigor to vegetation ; others are dissolv- 

 ed by moisture, and drained off by rain ; but these liqui- 

 factions are generally collected and turned to account. 

 To prevent, as far as possible, such losses, dunghills should 

 be sheltered from the atmosphere by sheds : these should, 

 however, remain open on the sides, as air in a moderate 

 quantity is required to promote fermentation. 



931. What is said of mud in the beds of rivers 1 932. And of 

 the elevation of temperature produced by the completion of fermentation"? 

 933. Of short manure! 934. Of long manure'? 935. Why 



should dunghills be sheltered'? 936. Why should the sheds be open at 

 the sides'? 



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