240 SCIENCE OF GARDENING. Part II. 



which carries from 1500 to 2000 cubical feet. It is used as a manure only in very 

 small quantities ; and particularly for crops of maize. Some experiments were made on 

 specimens of guano in 1805. It appeared as a fine brown powder ; it blackened by heat, 

 and gave off strong ammoniacal fumes ; treated with nitric acid, it afforded uric acid. 

 In 1806, Fourcroy and Vauquelin published an elaborate analysis of guano. They 

 state that it contains a fourth part of its weight of uric acid, partly saturated with am- 

 monia, and partly with potassa ; some phosphoric acid combined with the bases, and 

 likewise with lime. Small quantities of sulphate and muriate of potassa, a little fatty 

 matter, and some quartzose sand. ' It is easy to explain its fertilising properties : from 

 its composition it might be supposed to be a very powerful manure. It requires 

 water for the solution of its soluble matter to enable it to produce its full beneficial effect 

 on crops. 



1 144. The dung of sea-birds has never been much used as a manure in this country ; 

 but it is probable that even the soil of the small islands on our coast much frequented by 

 them would fertilise. Some dung of sea-birds, brought from a rock on the coast of 

 Merionethshire, produced a powerful, but transient effect on grass. The rains in our 

 climate must tend very much to injure this species of manure, where it is exposed to 

 them, soon after its deposition ; but it may probably be found in great perfection in 

 caverns or clefts in rocks haunted by cormorants and gulls. Some recent cormorants' 

 dung, when examined, had not at all the appearance of the guano ; it was of a greyish- 

 white color ; had a very fetid smell, like that of putrid animal matter ; when acted 

 on by quick-lime, it gave abundance of ammonia j treated with nitric acid, it yielded 

 uric acid. 



1 145. Night-soil, it is well known, is a very powerful manure, and very liable to de- 

 compose. It differs in composition ; but always abounds in substances composed of 

 carbon, hydrogen, azote, and oxygen. From the analysis of Berzelius, it appears that a 

 part of it is always soluble in water ; and in whatever state it is used, whether recent or 

 fermented, it supplies abundance of food to plants. The disagreeable smell of night- 

 soil may be destroyed by mixing it with quick-lime ; and if exposed to the atmosphere 

 in thin layers, strewed over with quick-lime in fine weather, it speedily dries, is easily 

 pulverised, and in this state, may be used in the same manner as rape-cake, and 

 delivered into the furrow with the seed. The Chinese, who have more practical know- 

 ledge of the use and application of manures than any other people existing, mix their 

 night-soil with one third of its weight of a fat marl, make it into cakes, and dry it by 

 exposure to the sun. These cakes, we are informed by the French missionaries, have no 

 disagreeable smell, and form a common article of commerce of the empire. The earth, 

 by its absorbent powers, probably prevents, to a certain extent, the action of moisture 

 upon the dung, and likewise defends it from the effects of air. Desiccated night-soil, in 

 a state of powder, forms an article of internal commerce in France, and is known under 

 the name of poudrette. In London it is mixed with quick-lime, and sold in cakes under 

 the name of " Clarke's desiccated compost." 



1146. Pigeons' dung comes next in order, as to fertilising power. 100 grains di- 

 gested in hot water for some hours, produced 23 grains of soluble matter, which 

 afforded abundance of carbonate of ammonia by distillation ; and left carbonaceous 

 matter, saline matter, principally common salt, and carbonate of lime as a residuum. 

 Pigeons' dung, when moist, readily ferments, and after fermentation, contains less 

 soluble matter than before ; from 100 parts of fermented pigeons' dung, only eight parts 

 of soluble matter were obtained, which gave proportionally less carbonate of ammonia in 

 distillation than recent pigeons' dung. It is evident that this manure should be applied 

 as new as possible ; and when dry, it may be employed in the same manner as the other 

 manures capable of being pulverised. The soil in woods, where great flocks of wood- 

 pigeons roost, is often highly impregnated with their dung, and it cannot be doubted, 

 would form a valuable manure. Such soil will often yield ammonia when distilled with 

 lime. In the winter, likewise, it usually contains abundance of vegetable matter, the 

 remains of decayed leaves, and the dung tends to bring the vegetable matter into a state 

 of solution. Manuring was, and still is, in great esteem in Persia. 



1 147. The dung of domestic fowls approaches very nearly in its nature to pigeons' dung. 

 Uric acid has been found in it. It gives carbonate of ammonia by distillation, and im- 

 mediately yields soluble matter to water. It is very liable to ferment. The dung of 

 fowls is employed, in common with that of pigeons, by tanners, to bring on a slight degree 

 of putrefaction in skins that are to be used for making soft leather ; for this purpose 

 the dung is diffused through water. In this state it rapidly undergoes putrefaction, and 

 brings on a similar change in the skin. The excrements of dogs are employed by the 

 tanner with similar effects. In all cases, the contents of the grainer, as the pit is called 

 in which soft skins are prepared by dung, must form a very useful manure. 



1 148. Rabbits' dung has never been analysed. It is used with great success as a manure 

 by some farmers, who find it profitable to keep rabbits in such a manner as to preserve 



