weight when it lived on spring water, and still more when its food was Thames water. Secondly, that the water they thus pass nourishes them merely as water, without taking any foreign substance into account, for 3000 grs. of rain water, in Dr. Woodward's experiment, afforded an increase of 17 grs., whereas by Margraaf's experiments, 5760 grs. of that water contain only d of a grain of earth: but, Thirdly, it also follows that water contributes still more to the nourishment of Plants, besides the service it renders them in distributing the nutritive parts throughout the whole structure, forming itself a constituent part of all of them, may be understood from modern experiments. Dr. Ingenhouz and M. Senebier have shewn that` the leaves of Plants exposed to the sun produced pure air. Now water has of late been proved to contain about 87 per cent. of pure air, the remainder being inflammable air; WATER IS THEN DECOм

POSED BY THE ASSISTANCE OF LIGHT WITHIN THE VEGETABLE, ITS INFLAMMABLE PART IS EMPLOYED IN THE FORMATION OF Oils, resins, gums, &C. ITS PURE AIR IS PARTLY APPLIED TO THE PRODUCTION OF VEGETABLE ACIDS, AND PARTLY EXPELLED AS EXCREMENT."

This last Theory will be found to accord with every practical observation, and must form the groundwork of every system of Horticulture, arranged on demonstrative principles that can be expected to be sustained with success.

Kirwan further states, "To Mr. Hazenfraz we owe the discovery, that coal is an essential ingredient in the food of all vegetables; though hitherto little attended to, it appears to be one of the primeval principles, as ancient as the present constitution of our globe, for it is found in fixed air, of which it constitutes above one fourth part, and fixed air exists in lime stones and other substances. which date from the first origin of things.

Coal not only forms the residuum of all vegetable substances that have undergone a slow and smothered combustion, that is, to which the free access of air has been prevented, but also of all putrid vegetable and animal bodies, hence it is found in vegetable and animal manures that have undergone putrefaction, and is the true basis of their ameliorating powers; if the water that passes through a putrifying dunghill be examined, it will be found of a brown colour; and if subjected to evaporation, the principal parts of the residuum will be found to consist of coal; all soils steeped in water communicate the same colour to it, in proportion to their fertility, and this water being evaporated, leaves also a coal, as Hazenfraz and. Fourcroy attest."

Sir Humphry Davy says, "No substance is more necessary to Plants than carbonaceous matter, and if this cannot be introduced into the organs of Plants, except in a state of solution, there is every reason to suppose that other substances less essential will be in the same case. I found by some experi

ments made in 1804, that Plants introduced into strong solutions of sugar, mucilage, tanning principle, jelly, and other substances died, but that Plants lived in the same solutions after they had fermented. At that time I supposed that fermentation was necessary to prepare the Food of Plants, but I have since found that the deleterious effects of the recent vegetable solutions were owing to their being too concentrated, in consequence of which, the vegetable organs were wholly clogged with solid matter, and the transpiration of the leaves prevented; the beginning of June in the next year, I used solutions of the same substances, but so much diluted that there was only about one two-hundredth part of solid vegetable matter in the solutions. Plants of Mint grew luxuriantly in all those solutions, but least so in that of astringent matter; I watered some spots of grass in a garden with the different solutions of jelly, sugar, and mucilage, which grew most vigorously, and that watered with the solution of tanning principle grew better than that watered with common water."

This experiment certainly shews the fertilizing powers of those vegetable substances, but as the decomposition of such substances spontaneously takes place in so short a time, I think it most probable, that Sir Humphry's first idea was a correct one, and that they were reduced by fermentation to the common state of manures, before they became ap

* A very singular conclusion this.

plicable, and that with the concentrated solutions the accumulated gas resulting from the ferment ation destroyed the vegetables; or as Kerwan remarks, 66 Vegetables not only require Food, but that this Food be duly administered to them, a surfeit being as fatal to them as absolute privation."

And further," Hazenfraz and Fourcroy attest, that shavings of wood being left in a moist place for nine or ten months, began to receive the fermentative motion, and being then spread on land, putrefied after some time, and proved an excellent manure. Coal however cannot produce its beneficial effects, but inasmuch as it is soluble in water, the means of rendering it soluble are not as yet well ascertained, nevertheless it is even now used as a manure and with good effect."

"In truth, the fertilizing power of putrid animal and vegetable substances were pretty fully known even in the remotest ages, but most Speculatists have hitherto attributed them to the oleaginous, mucilaginous, or saline particles then developed, forgetting that land is fertilized by paring and burning, though the oleaginous and mucilaginous particles are thereby consumed or reduced to a coal, and the quantity of mucilage, oil, or salt in fertile land is so small, that it could not contribute the 1000th part of the weight of any vegetable, whereas coal is not only supplied by the land, but also by fixed air combined with the earths, and also by that which is constantly let loose by various processes, and soon precipitates by superiority of its specific

gravity, and is then condensed in, or mechanically absorbed by soils, or contained in dew.”

This corroborates my preceding observations, and exhibits a difference in the opinions of those authors, but it is of no great importance, as Sir Humphry Davy also says, Mucilaginous, gelatinous, saccharine, oily, and extractive fluids, and solution of carbonic acid in water, are substances that in their unchanged states contain almost all the principles necessary for the life of plants; but there are few cases in which they can be applied as manures in their pure forms, and vegetable manures in general contain a great excess of fibrous and insoluble matter, which must undergo chemical changes before they become the Food of Plants."

I cannot think any case ever existed where such fluids were taken up as Food in an unchanged state, but that the fluids as well as the fibrous parts, must previously undergo chemical changes.

On earths Kirwan says, "The next most important ingredient to the nourishment of Plants is earth, and of the different earths the calcareous seems the most necessary, as it is contained in rain water, and absolutely speaking many Plants may grow without imbibing any other. M. Ruckert is persuaded that earth and water, in proper proportions, form the sole nutriment of Plants. But M. Giobert has clearly shown the contrary; for having mixed pure earth of alum, silex, calcareous earth, and magnesia in various proportions, and moistened them with water, he found that no grain would

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