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ing, had presented to the Institution the sum of £20 for the purchase of Scientific Apparatus.*

They further reported that the Secretary had received the following letter from SAMUEL REYNOLDS SOLLY, Esq. F.R.S. M.R.I. :—

10, Manchester Square, April 17, 1863.

"Dear Sir, "I beg to enclose you a cheque for £20, which I will thank you to give to the Treasurer of the Royal Institution, and to state, that I intend paying the same sum every year during my life; my wish being, that the money be applied in the same way as the donation of £40 by Sir Henry Holland.

"I remain, very faithfully yours,
66. S. R. SOLLY.

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The Treasurer announced, That Sir HENRY HOLLAND, Bart. had again presented the sum of Forty Pounds, being his Fifth Annual Donation for the purchase of Scientific Apparatus.†

The following Professors were elected :

WILLIAM THOMAS BRANDE, Esq. D.C.L. F.R.S. Hon. Professor of Chemistry.

JOHN TYNDALL, Esq. F.R.S. Professor of Natural Philosophy.

EDWARD FRANKLAND, Esq. Ph.D. F.R.S. was elected Professor of Chemistry.

The PRESENTS received since the last Meeting were laid on the table, and the thanks of the Members returned for the same: viz.—

FROM

1863.

Astronomical Society, Royal-Monthly Notices, March, 1863. 8vo.
British Meteorological Society-Proceedings, Nos. 5, 6. 8vo.
Chemical Society-Quarterly Journal, New Series, No. 4. 8vo.
Civil Engineers, Institution of--Proceedings, April, 1863.

8vo.

1863.

Dircks, Henry, Esq. (the Author)-Contribution towards a History of ElectroMetallurgy. 16to. 1863.

Editors-Artizan for April, 1863. 4to.

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Practical Mechanics' Journal for April, 1863. 4to.

St. James's Medley for May, 1863.

Technologist for April, 1863.

8vo.

Franklin Institute of Pennsylvania-Journal, No. 447. 8vo. 1863.

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4to.

1862.

Geographical Society, Royal-Proceedings, Vol. VII. No. 2. 8vo. 1863.
Geological Institute, Vienna-Jahrbuch, Band XII. No. 4.
Horticultural Society, Royal-Proceedings, 1863. No. 4. 8vo.
Linnean Society--Transactions, Vol. XXIII. Part 3; Vol. XXIV. Part 1.

1862-3.

4to.

Manchester Literary and Philosophical Society-Proceedings, 1862-3. Nos. 1-12.

8vo.

1863.

Mechanical Engineers, Institution of-Proceedings, 1862. Part 3. 8vo. 1863.
Medico-Chirurgical Society, Royal-Proceedings, Vol. IV. No. 3.
Newton, Messrs.-London Journal (New Series) for April, 1863.

8vo. 8vo.

Petermann, A. Esq. (the Editor)-Mittheilungen aus dem Gesammtgebiete der Geographie. No. 3. 4to. 1863.

Photographic Society-Journal, No. 132. 8vo. 1863.

Silliman, Professor-American Journal of Science, &c. for April, 1863. 8vo.

WEEKLY EVENING MEETING,

Friday, May 8, 1863.

SIR RODERICK I. MURCHISON, K.C.B. D.C.L. F.R.S. Vice-
President, in the Chair.

DR. AUGUSTUS VOELCKER, F.C.S.

CONSULTING CHEMIST OF THE ROYAL AGRICULTURAL SOCIETY OF ENGLAND.

On some Chemical and Physical Properties of Soils, and the Productive Powers of the Soils of England.

In all fertile soils we find variable quantities of organic matter-readyformed ammonia, nitric acid, potash, soda, lime, magnesia, oxides of iron, chlorine, phosphoric, sulphuric, and silicic acids; in short, all the mineral matters which are found in the ashes of plants. These minerals, or ash-constituents, it need scarcely be observed, are not merely accidental but essential materials, without a proper supply of which no plant can grow luxuriantly and come to full maturity. In one sense all are equally important; for the absence or deficiency in the soil of one, be it lime or potash, phosphoric or silicic acid, is detrimental to the luxuriant development of the vegetable organism. No one who has given the slightest consideration to this subject will hesitate to give assent to this mineral theory.

It is natural to connect the productiveness of soils with the proportion of ash-constituents of plants which they contain; but although in some cases a soil may be unproductive on account of the absence or deficiency of lime or potash or phosphoric or any other mineral matter which enters into the composition of plants, in the majority of

cases the chemical analysis of different soils affords little or no indication of their relative productive powers.

The combinations in which the mineral constituents of plants exist in the soil, their unequal or uniform distribution in the surface, the composition and physical condition of the subsoil, the relative depth of both, the porosity of the land, and especially the power of absorbing and retaining, as well as modifying in a variety of ways the crude manuring agents which are applied to the land, unquestionably are intimately connected with the great variations which we notice in the agricultural capabilities of different soils.

Before the publication of Liebig's celebrated "Chemistry in its Application to Agriculture," a work which has given the death-blow to the humus theory, the fertility or barrenness of a soil was generally considered to depend entirely upon its physical properties and the presence or deficiency of humus. Soon after the publication of Liebig's writings, scientific men fell into the opposite extreme, and expected the bare chemical analysis of a soil and the ash-analyses of plants would enable them to discover at once the means of restoring the fertility of land, or to improve it by certain purely mineral manuring mixtures, and to grow on it, irrespective of its natural adaptation to the growth of particular crops, any kind and almost every amount of agricultural produce.

These unphilosophical views have rendered agricultural chemistry less popular than formerly, but also more scientific and more directly useful to the enlightened agriculturist.

A new direction to chemico-agricultural inquiries was given about ten years ago by Professor Way's highly important researches on the absorptive powers of soils for manure. Professor Way's investigations originated in an observation of Mr. Thompson, of Kirby Hall, York, who found that soils have the faculty of separating ammonia from its solution.

On passing solutions of ammonia through different soils, Way found that all possess the power of retaining ammonia, some more, some less. He also observed that potash, lime, magnesia, and phosphoric acid are absorbed by all soils to a considerable extent.

Still more important are his experiments, which prove that cultivated soils not only absorb free alkalies and acids, but have likewise the power of separating ammonia, potash, and other bases from their saline combinations.

Professor Way principally operated with simple salts it may therefore be urged, that it by no means follows, as a necessary consequence, that because a soil absorbs ammonia when a solution of sulphate of ammonia is passed through it, the same absorption will take place when an ammoniacal salt mixed with some dozen other substances is filtered through it.

I therefore operated with complex liquids, and already, in 1857, published several filtration experiments in the Journal of the Royal Agricultural Society.

These and many subsequent experiments have shown that all soils not only possess the power of absorbing and retaining potash, ammonia, phosphoric and silicic acid, and other mineral matters, but also of modifying in the most varied way the composition of complex saline solutions which are passed through them.

The following Table shows the results obtained in filtering the same kind of liquid manure through two very different soils :—

COMPOSITION of LIQUID MANURE before and after Filtration through Two Soils from the Neighbourhood of Cirencester.

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The preceding analytical results, amongst other particulars, show :

1. That the calcareous clay soil absorbed about six times as much ammonia from the liquid manure, as the sterile sandy soil.

2. That the liquid manure in contact with the calcareous clay soil, becomes much richer in lime; whilst during its passage through the sandy soil, it becomes purer in lime.

3. That the calcareous soil absorbed much more potash than the sandy soil.

4. That chloride of sodium, in conformity with the results of other observers, was not absorbed to any extent by either soil.

5. That both soils removed from the liquid most of the phosphoric acid.

6. That the liquid in passing through the calcareous soil becomes

poorer; and, on the other hand, in passing through the sandy soil becomes richer in soluble silica.

The property of soils to store up food for plants is thus not confined to one particular kind of fertilizing matter, but it applies to them all, and manifests itself in a way which is modified by the composition of the soil.

In these, and in all other experiments which I have since made, the ammonia, potash, phosphoric acid, and other fertilizing matters contained in a solution were never completely absorbed by any soil, however weak or concentrated the solutions were that were filtered through the soil. Indeed, if the solution of saline matters which are brought into contact with soil are very dilute, scarcely any absorption of ammonia, potash, or phosphoric acid takes place.

Sewage of towns, on account of the very diluted condition in which this liquid is usually found, in percolating through a soil scarcely leaves any of its soluble constituents in the soil in a fixed or less soluble form, although the soil possesses in a high degree the power of absorbing and retaining soluble fertilizing matters.

All soluble saline matters, however useful or necessary they may be, impede the rapid growth of plants if they are presented too abundantly or in too concentrated a solution to the roots of plants. One of the functions of the soil appears to be to transform such readily soluble compounds into combinations so little soluble in water, that they pass in common life as insoluble, but which are still sufficiently soluble to supply the growing plant with the necessary amount of mineral food in a state of solution.

This beautiful power of soils thus not only effectually prevents the waste in fertilizing matters which heavy rains would otherwise occasion, but also rectifies in a great measure any misapplication which may be made of concentrated soluble fertilizers.

The power of soils to modify manuring matters depends in a great measure on the chemical composition of the soil, and also on the concentration of the liquid and the quantity of soluble fertilizing matters which is incorporated with that portion of the soil which is penetrated by the roots of plants. Hence the effect which one and the same manure is capable of producing varies greatly in different soils, and also with a rainy or dry season.

The office of the soil is not merely to supply mineral food to plants, but also to manufacture, so to say, crude food into a condition fit for assimilation; to prevent injury to the living plant by too large an accumulation of soluble matters in the surface soil; to store up for future use such an excess; to diffuse it equally in that portion of the land reached by the roots of plants; and to modify it in conformity with the requirements of our crops, in a manner differing with each description of land.

Respecting the causes of the absorbing properties of soils, the opinions of chemists are divided.

VOL. IV. (No. 38.)

I

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