Wiklund, &c.; whilst a vast storehouse of data of information for future use has been accumulated, and is being yearly accumulated, in the field experiments of Lawes and Gilbert, at Rothamsted, followed up by those of late years carried on at Wobnrn by A. Voelcker and J. A. Voelcker. Most of the memoirs touching these subjects published by the various authors have: however, had to do rather with manures than directly with soils, and for the moment it is proposed to select for CORsideration such work as has borne more directly on the question of soil analysis, so far as concerns phosphoric acid and potash. The memoirs coming strictly under this head to be found in modern chemical literature are comparatively few. The earliest paper of any importance that the author has been able to find is that of 3. v. Liebig (Zeitschrift d. Landwirth. Vereines, 1872), who worked on soils obtained from the permanent wheat field at Rothamsted. The attention of the present author was directed to Liebig's investigation by Dr. (now Sir J. Henry) Gilbert, when some three or four years ago he discussed with him the lines on which it was proposed to pursue the investigation which forms the principal subject of the present paper. I n the light of the results of the experiments since made with soils from other Rothamsted plots, plots not only more numerous, but experimentally nearly twenty yeare older, than those worked on by Liebig in 1872, it appears to be desirable to quote here some of Liebig's figures. The specimens of soil used by Liebig were from Broadbalk WheaG field, Rothamsted, and represented the 1st and 2nd depths of 9 inches each. No. 3 soil had been continuously unmanured for nearly thirty years. Liebig determined in it several of the mineral constituents solnble in L ' dilute hydrochloric acid'' and in " dilute acetic acid." As the present paper is concerned only with potash and phosphoric acid, it is unnecessary to quote Liebig's determinations of lime, magnesb, soda, &c. The other soils were 10 A, which for nearly 30 years had received an annual dressing of 400 lbs. ammonia salts, without mineral manure ; 5 A, which for a like time had received a complete annual dressing of mineral manures, without nitrogen ; 7 A, which had received annually both 400 lbs. ammonia salts and a complete mineral manure; and 2, which had received an annual dressing of 14 t~n s of farmyard manure. K 2

At the time these experiments were undertaken, the author was unaware of the work of Dafert (Landwirth-~ersuchs., 34), and of the later work of Arnold and Wedermeyer (Zeit. A n a l. Chem., 31, 525) in the same direction. On the whole, the experience of these authors is similar in most direct,ions to that now recorded, although the majority of' the representalive compounds selected for their experiments were different from those used by the present author.

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