nitrogen, that is to say, the useful substances found in any serviceable manure, compost, etc., from time immemorial. They are in a condensed form, nearly constant in composition, and may be readily mixed in various proportions to suit the nature of the desired crop, or the degree of the natural fertility of the soil. Moreover, with them, the farmer will be less exposed to frauds than when he buys manures already mixed, which, too often, are but nondescript compounds. Manuring with chemicals alone has been proved by Prof. Ville and his followers to be profitable; nevertheless, other manures and compounds may be used in connection with them, but their usefulness as plant food will be in the ratio of the phosphorus, lime, potassa, and nitrogen which they contain in the soluble or available state. When once the farmer has arrived at a knowledge of the natural fertility of his farm by the aid of experimental fields, as explained in this work, he will be able to compound his manures for each desired crop, without expending money for what is already in the soil, or omitting what is wanting. How much more desirable to do so, and to work with certainty, than to buy already mixed manures from the manufacturer, who, supposing that he is honest, can certainly know little, if anything, about the natural fertility of the soil, the previous manuring, or the rotation of crops on the farm of the purchaser. This little book, written in a familiar dialogistic form, and intended for popular use, is a résumé of several larger works by the same author. We hope that it will be found interesting and useful, not only by farmers, but also by all those persons who have a fondness for agriculture. PHILADELPHIA, June, 1872. NOTE. A. A. F. The French metric decimal weights, measures, and values have been retained in this translation for the sake of clearness and facility in comparing together the various formulæ and results of experiments. Moreover, the money values given in this work, if translated into American currency, would not answer the American market prices of the various substances. For those desirous of transforming into English the French weights, measures, and values mentioned in this work, we give the following tables : 1 hectolitre 1 kilogramme 1 tonne (ton) 1 franc =3.5316 cubic feet. = 2.8379 U. S. bushels of 2150.42 cubic inches. = 2.2055 lbs. avoirdupois. 1000 kilogrammes. = 2205.486 lbs. avoirdupois. As a means of converting quantities and values as applied to the hectare into the corresponding quantities and values per acre, the following table will be found useful: CONTENTS. The suppression of one of these substances is suffi- |