the description of lands which are most likely to be benefited by its application.

The EIGHTH LECTURE concludes the subject of the chemistry of agriculture, by establishing the theory of the operation of burning lands: he considers the process to be useful in rendering the soil less compact, and less tenacious and retentive of moisture; and that, when properly applied, as being capable of converting a matter that was stiff, damp, and cold, into one powdery, dry, and warm, and much more proper as a bed for vegetable life. He states the great objection made by speculative chemists to paring and burning, to be the unavoidable destruction of vegetable and animal matter, or the manure of the soil; but he considers that, in those cases in which the texture of its earthy ingredients is permanently improved, there is more than a compensation for so temporary a disadvantage; and that in some soils, where there is an excess of inert vegetable matter, the destruction of it must be beneficial, and that the carbonaceous matter remaining in the ashes may be more useful to the crop than the vegetable fibre from which it was produced.

In this view of the subject it is evident, that all poor siliceous sands must be injured by the operation; " and here," says Davy, "practice is found to accord with theory. Mr. Arthur Young, in his Essay on Manures, states, that he found burning injure sand;' and the operation is never performed by good agriculturists upon siliceous sandy soils, after they have been once brought into cultivation. An intelligent farmer in Mount's Bay told me, that he had pared and burned a small field several years ago, which he had not been able to bring again into good condition. I examined the spot,-the grass was very poor and scanty, and the soil an arid siliceous sand." Irriga tion, or watering land, is a practice, he observes, which at first view appears the reverse of torrefaction; and, in general, the operation of water in nature is to bring earthy substances into an extreme state of division. But in the artificial watering of meadows, the beneficial effects may depend upon many different causes, some chemical, some mechanical. It may act as a simple supply of moisture to the roots, or it may carry into the soil foreign matter, or diffuse that which exists in it more equally through its substance.

He concludes with some valuable scientific observations upon the process of fallowing, by which he attempts to correct the prejudices which have existed with regard to its benefits. He points out, on the other hand, the great advantages of the convertible system of husbandry, by which the whole of the manure is employed; and those parts of it which are not fitted for one crop,

remain as nourishment for another. These views he illustrates by a reference to the course of crops adopted by Mr. Coke, in which "the turnip is the first in the order of succession; and this crop is manured with recent dung, which immediately affords sufficient soluble matter for its nourishment; and the heat produced in fermentation assists the germination of the seed and the growth of the plant. After turnips, barley with grass seeds is sown; and the land having been little exhausted by the turnip crop, affords the soluble parts of the decomposing manure to the grain. The grasses, rye-grass, and clover remain, which derive a small part only of their organized matter from the soil, and probably consume the gypsum in the manure which would be useless to other crops: these plants likewise, by their large system of leaves, absorb a considerable quantity of nourishment from the atmosphere, and when ploughed in at the end of two years, the decay of their roots and leaves affords manure for the wheat crop; and at this period of the course, the woody fibre of the farm-yard manure, which contains the phosphate of lime and the other difficultly soluble parts, is broken down; and as soon as the most exhausting crop is taken, recent manure is again supplied."

At the end of his system is added an Appendix, containing An Account of the results of experiments on the produce and nutritive qualities of the grasses and other plants used as the food of animals; instituted by John Duke of Bedford." But as these experiments do not admit either of abridgement or analysis, the reader must refer to the original source for information.

I shall conclude this long, and I fear somewhat tedious review, with the animated appeal so earnestly addressed by the illustrious author to the philosophical readers of his work.

"I trust that the enquiry will be pursued by others; and that in proportion as chemical philosophy advances towards perfection, it will afford new aids to agriculture; there are sufficient motives connected both with pleasure and profit, to encourage ingenious men to pursue this new path of investigation. Science cannot long be despised by any persons as the mere speculation of theorists, but must soon be considered by all ranks of men in its true point of view, as the refinement of common sense guided by experience, gradually substituting sound and rational principles for vague popular prejudices.

66

The soil offers inexhaustible resources, which, when properly appreciated and employed, must increase our wealth, our population, and our physical strength.

"We possess advantages in the use of machinery, and the division of

labour, belonging to no other nation. And the same energy of character, the same extent of resources, which have always distinguished the people of the British Islands, and made them excel in arms, commerce, letters, and philosophy, apply with the happiest effects to the improvement of the cultivation of the earth. Nothing is impossible to labour, aided by ingenuity. The true objects of the agriculturist are likewise those of the patriot. Men value most what they have gained with effort; a just confidence in their own powers results from success; they love their country better, because they have seen it improved by their own talents and industry; and they identify with their interests, the existence of those institutions which have afforded them security, independence, and the multiplied enjoyments of civilized life."

CHAPTER X.

Mr. Faraday's introduction to Sir H. Davy.-A renewed correspondence on the subject of the Gunpowder Manufactory.-Davy obtains permission from Napoleon to visit the Continent.—He embarks in a Cartel from Plymouth. - Is arrested at Morlaix.-Arrives at Paris.-Visits the Louvre. His extraordinary conduct upon that occasion.-Inspects the Colossal Elephant, and is introduced to M. Alavair, its architect.-The discovery of the dungeons of the Bastile.Davy's interesting letter to M. Alavair. He attends a meeting of the Institute.-Is visited by all the principal savans of Paris.-The adventure which befell Lady Davy in the Thuilleries' Garden. -Anniversary dinner of the Philomatic Society. The junior Chemists of France invite Davy to a splendid entertainment.—How far Davy is entitled to be considered the discoverer of the true nature of Iodine.-Napoleon's unlucky experiment with the Voltaic battery.—Davy is presented to the Empress Josephine.-An account of the Court ceremony at Malmaison.-Remarks on the conduct of Davy during his visit to Paris. He quits the capital of France, and proceeds, by way of Lyons, to Montpellier.-Is assisted in experiments on sea-weed by M. Berard. Crosses the Alps.-Arrives at Genoa.-Institutes experiments on the Torpedo.-Visits Florence, and accomplishes the combustion of the diamond, by the great lens in the cabinet of Natural History.-Experiments on Iodine.-He examines the colours used by the Ancients.— Visits all the celebrated Philosophers of Italy and Switzerland, with whom he works in their laboratories. Returns to England.

It is said of Bergman, that he considered the greatest of his discoveries to have been the discovery of Scheele.* Amongst the numerous services conferred upon Science by Sir Humphry Davy, we must not pass unnoticed that kind and generous patronage which first raised Mr. Faraday from obscurity, and gave to the chemical world a philosopher capable of pursuing that brilliant path of enquiry which the genius of his master had so successfully explored.

The circumstances which first led Mr. Faraday to the study of chemistry, and by which he became connected with the Royal Institution, were communicated to me, by himself, in the following letter.

* See Note at page 31.

TO J. A. PARIS, M. D.

MY DEAR SIR,

Royal Institution, Dec. 23, 1829. You asked me to give you an account of my first introduction to Sir H. Davy, which I am very happy to do, as I think the circumstances will bear testimony to his goodness of heart.

When I was a bookseller's apprentice, I was very fond of experiment, and very averse to trade. It happened that a gentleman, a member of the Royal Institution, took me to hear some of Sir H. Davy's last lectures in Albemarle Street. I took notes, and afterwards wrote them out more fairly in a quarto volume.

My desire to escape from trade, which I thought vicious and selfish, and to enter into the service of Science, which I imagined made its pursuers amiable and liberal, induced me at last to take the bold and simple step of writing to Sir H. Davy, expressing my wishes, and a hope that, if an opportunity came in his way, he would favour my views; at the same time, I sent the notes I had taken at his lectures.

The answer, which makes all the point of my communication, I send you in the original, requesting you to take great care of it, and to let me have it back, for you may imagine how much I value it.

You will observe that this took place at the end of the year 1812, and early in 1813 he requested to see me, and told me of the situation of assistant in the Laboratory of the Royal Institution, then just vacant.

At the same time that he thus gratified my desires as to scientific employment, he still advised me not to give up the prospects I had before me, telling me that Science was a harsh mistress; and, in a pecuniary point of view, but poorly rewarding those who devoted themselves to her service. He smiled at my notion of the superior moral feelings of philosophic men, and said he would leave me to the experience of a few years to set me right on that matter.

Finally, through his good efforts I went to the Royal Institution early in March of 1813, as assistant in the Laboratory; and in October of the same year, went with him abroad as his assistant in experiments and in writing. I returned with him in April 1815, resumed my station in the Royal Institution, and have, as you know, ever since remained there.

I am, dear Sir, very truly yours,

M. FARADAY.