As ammonia is one of the compounds specially given off by putrifying animal substances, it is not unlikely that a watering with _ammoniacal liquor_ would materially prepare the peat for undergoing fermentation. At all events it seems possible to prepare any quantity of valuable peat compost by mixing the peat with a still less quantity of fermented manure than was employed by Lord Meadowbank, provided the liquid manure of the farm-yard be collected in a cistern, and be thrown at intervals by means of a pump over the prepared heaps. One important use also to which I think peat may be applied is, after it is partly dried, to build it into covered heaps, and half burn or char it till it become readily reducible into a fine powder. In this state it would be of great value as a mixture to preserve the virtues of liquid manures of all kinds, of night-soil, and of ammoniacal liquor. SECTION III.—RELATIVE VALUE OF DIFFERENT VEGETABLE MANURES. There are two principles on which the relative value of different vegetable substances, as manures, may be stated to depend—_first_, on the relative quantity and kind of _inorganic matter_ they contain; and _second_, on the relative proportions of _nitrogen_ present in each. 1. Valued according to the _quantity_ of inorganic matter they contain—the worth of the several kinds of straw and hay would be represented by the following numbers:— Wheat straw, 70 to 360 Oat straw, 100 to 180 Hay, 100 to 200 Barley straw, 100 to 120 Pea straw, 100 Bean straw, 60 to 80 Rye straw, 50 to 70 Dry potato tops, 100 Dry turnip tops, 260 Rape, cake, 120 that is, a _ton weight_ of each of these substances, when made into manure—provided nothing is washed out by the rains—will return to the soil the above quantities of inorganic matter _in pounds_. Generally, perhaps, these numbers will give the reader an idea of the relative _permanent_ effect of these different kinds of vegetable matter when laid upon the soil. But, by a reference to the facts stated in pp. 58 to 64, in regard to the _quality_ of the inorganic matter contained in plants, he will satisfy himself, that the effect of these manures on particular crops is not to be judged of solely by the absolute quantity of earthy and saline matter they contain;—that which the turnip-top, for example, or the bean-stalk, returns to the soil, may not be exactly what will best promote the growth of wheat. 2. On the other hand, if the fertilizing value of vegetable substances is to be calculated by the relative quantities of nitrogen they severally contain, we should place them in the following order:—the number opposite to each substance representing that weight of it in pounds, which would produce the same effect as 100 pounds of farm-yard manure, consisting of the mixed droppings and litter of cattle.