Attempts have been made to dry this manure also, so as to render it more portable,—to destroy its unpleasant smell, so as to reconcile practical men to a more general use of it,—and by certain chemical additions, to prevent the waste of ammonia and other volatile substances, which are apt to escape and be lost when this and other powerful animal manures begin to putrify through decay. In Paris, Berlin, and other large cities, the night-soil, dried first in the air with or without a mixture of gypsum or lime, then upon drying plates, and finally in stoves, is sold under the name of _poudrette_, and is extensively exported in casks to various parts of the country. In London also it is dried with various mixtures, while in others of our large towns an _animalized charcoal_ is prepared by mixing and drying night-soil with gypsum and ordinary wood charcoal in fine powder. The half-burned peat above described (p. 80,) would answer well for such a purpose, while few simple and easily attainable substances would make a better compost with night-soil, and more thoroughly preserve its virtues, than half-dry peat or rich vegetable soil, mixed with more or less marl or gypsum. It is impossible to estimate the proportion of waste which this valuable manure undergoes by being allowed to ferment, without mixture, in the open air. _Taffo._—In China it is kneaded into cakes with clay, which are dried in the air, and, under the name of taffo, form an important article of export from all the large cities of the empire. _Pigeons’ Dung._—The dung of all birds is found to possess eminent fertilizing virtues. Some varieties are stronger than others, or more immediate in their action, and all are improved for the use of the farmer by being some time kept, either alone or in compost. In Flanders the manure of one hundred pigeons is considered worth 20s. a year for agricultural purposes. _Guano_ is the name given by the natives of Peru to the dung of sea-fowl, which in former periods used to be deposited in vast quantities on the rocky shores and isles of the Peruvian coast. The numerous shipping of modern times has disturbed and driven away many of the sea-fowl, so that comparatively little of their recent droppings is now preserved or collected. Ancient heaps of it, however, still exist in many places, more or less covered up with drifted sand, and also more or less decomposed. These are now largely excavated for exportation, not only to different parts of the coast of Peru, as seems to have been the case from the most remote periods, but also to Europe, and especially to England. It is at present sold at 20s. a cwt. in this country, and is capable of entirely replacing farm-yard dung,—that is to say, turnips may be manured successfully with guano alone;—but it has not yet been satisfactorily determined that the English farmer can afford to use it in this way to any extent, at the price now asked for it.