Without referring to the analogy, which could be easily proved to be incorrect, and a weak and inefficient prop to the argument, I think I shall have little difficulty in convincing you and the public, that the comparative experiment, although it was apparently conclusive, yet, was incomplete and unsatisfactory; inasmuch as no use appears to have been made of the thermometer, for ascertaining the comparative degree of heat of the soil, in the portions of the field when manured in the manner already described, both when the turnip seed was sown, and at different periods of the growth of the plants. To this neglect, I conceive may be attributed the fallacy of the conclusions, which have been deduced from so well planned an experiment.

I am aware that, in opposing the opinions of so truly philosophical an enquirer into vegetable physiology as Mr. Knight is, I expose myself to the hazard of being stigmatized with presumption; but, I am also convinced, that as truth alone is the object of that gentleman's researches, he will receive with candour any objections to his opinions which are fairly advanced. I have, therefore, no hesitation in asserting, that before we can admit the correctness of the opinion, which assumes that the superiority of the crop, on the portion of the field manured with the green fern, was owing to the more easy re-organization of the recent vegetable matter employed as manure, by the living powers of the growing plants, the author of it is bound to demonstrate how any vegetable substance contained in the soil, in a state not reduced to its ultimate components, can be taken up by the absorbents of the radicles of plants; and, also, how any vegetable substance, without being so reduced, can be rendered sufficiently soluble in the soil to enter the mouths of these minute vessels? I am willing to admit that the secretions of some plants are altered by situation, and the nature of the soil in which they grow as for example, in the change from potash to soda, which occurs in plants brought from inland situations and cultivated near the sea. But, it must be remarked, that these changes are found to occur in the saline secretions only, which are remarkably soluble. Linnæus, indeed, maintained, that the secretions of plants very different from one another in genera and species, growing on the same soil, exist ready prepared in the earth, and are merely selected by the plants: but this opinion has been long since regarded as untenable. The living powers of both animals and plants seem to be perfectly adapted for recombining substances the most opposite and incongruous, and assimilating them to their own proper nature. What can be stronger proofs of this fact, than that

the Cobra de Capelho secretes the poison which is found under its fang, from aliment which is not essentially different from that employed by the most innocuous of the serpent tribe; and that fruit, which is sweet, palatable, and nutritious, is the product of the same soil as the most bitter, nauseous, and poisonous plants? or that, in the same animal and plant, secretions are found possessed of properties almost diametrically opposite? It is a fact, well known to physiologists, that chyle, the substance produced by the change which the food undergoes, before it mingles with the blood, has no analogy with the character of the food from which it is formed, but derives its peculiar properties from the action of the glands of the mesentery by which it is prepared. Whether this be the case with the sap of plants, which may be regarded as the chyle of vegetables, we shall never, perhaps, be able to ascertain, owing to the impossibility of obtaining it unmixed with some of the ready formed secretions, previously deposited in or near the root of the plant; but, from the known characters of sap, as it has been procured, we know that it varies much less in different plants than we might à priori expect, on viewing the great diversity of their secretions. That it is not, therefore, requisite for the vigorous growth of plants to manure the soil with fresh-vegetable matter, in order to enable the plants to obtain their food in a state the least changed, and decomposed by putrefaction, is obvious; but it must, at the same time, be admitted, that fresh-vegetable matter employed as manure is admirably adapted to advance vegetation; and the following appears to me to be the true explanation of this fact, and the cause of the great superiority of the crop, on the portion of the field manured with the green Fern alluded to in Mr. Knight's experiment.

One of the most striking, and the most universally known, of the phenomena of the process of fermentation, is the extrication of heat; and this principle, also, is the most powerful and healthful stimulus of the vegetable excitability, when it is not applied in excess. Now, the disposition of green or recent vegetable matter to run into rapid fermentation is well known; and it is easy to conceive, that matter of this description, placed under the soil so as to retain a considerable degree of moisture, is in a situation the most favourable for commencing and carrying on the process of fermentation; thence, the more recent the vegetable substance, the sooner will the extrication of heat commence, and the longer will it be given out. The surrounding soil, also, not being of a combustible nature, and not a very good conductor of caloric, the heat will spread in a more equable degree; while,

the rapidity of the fermentation will be so moderated, as to prevent the pabulum of the process, if I may so express myself, from being too soon exhausted. Owing to this state of the green Fern, therefore, the germination of the turnip seed sown over it was begun, and the vegetative process carried on in the plants, in a manner somewhat similar to the effect which would follow were the seed sown in a hot-bed; except that the heat was of a more moderate degree, and, consequently, better suited to maintain the functions of the vegetable economy in the growing plant in a healthy state. The fold and stable manure, on account of the ready formed salts it contained, would, perhaps, promote the germination of the seed and the growth of the plants more vigorously for a short time; but as the process of fermentation would be sooner completed in it than in the green Fern, the supply of heat to the soil would be sooner exhausted, and consequently, that necessary stimulus being withdrawn from the growing turnips on the portion of the field manured with it, the plants over the green Fern would now gain the ascendancy, as they were still supplied with heat; the process of decomposition being yet in activity in the Fern. Again, as the fermentation was altogether over in the completely decayed dung, no heat, or scarcely any, would be extricated from it, and, therefore, the sole benefit which could arise to the germinating seeds and growing plants from this manure, must have proceeded merely from the stimulus of its saline components, and from the carbonaceous matter in a soluble state, which it is adapted to afford. It may be argued, that, as it is probable, the soluble carbonaceous matter afforded by completely decayed dung is the chief part of the food of plants, the turnips raised over this manure should contain more solid contents than those over the other manures, although their growth was less vigorous and luxuriant. That, however, more food is supplied by completely decayed manure, and yet less taken into the system of the plant, may be equally true; for the heat afforded by the more recent manures being absent, the action of the vegetable vessels in the growing turnips would be more languid, and absorption and assimilation consequently less perfect; the presence of the stimulus of heat being as essential as the simple supply of nutriment, for the perfection of the plant. That it is heat only which can be regarded as the agent producing the superiority of the crop of turnips, on the portion of the field manured with green Fern, as detailed in Mr. Knight's experiment, may easily be proved by the thermometer, in a repetition of the experiments. Why, therefore, Mr. Knight may say, has the objector to my ex

planation not maintained the truth of his objections by experiments with that instrument. I reply that, in the first place, my residence in town and my professional avocations, oppose themselves to any experimental attempt of the kind; and, in the second place, that any experiments on my part are unnecessary, as I admit the accuracy of Mr. Knight's experiments, and differ from him only in the conclusions which he has deduced from them. Our premises are the same, but our conclusions are at variance, and, it must remain with others to decide which are the most accurate, and as the discovery of truth is the object of both, the determination will be equally acceptable, whatever may be the decision.

In the supposition that my opinions of the effects of these manures are correct, it would appear, that the most useful manure may be obtained from a mixture of completely decayed stable or fold litter, and green or fresh vegetable matter; or perhaps no manure would be more efficient than green vegetable matter spread under the soil, and a top dressing of salt and soot. The completely decayed manure would produce its effect by affording soluble carbonaceous matter and salts as food and stimuli to the growing plants, whilst the heat extrcated by the fermentation of the green-vegetable manure, would supply a sufficiency of that principle which, in conjunction with air and moisture, is absolutely necessary for rousing into activity the vital energies latent in the seed, and maintaining in the future plant the proper exercise of those functions, which enable it to select and absorb its nutriment from the soil, to carry it through its system of vessels and glands; to concoct and secrete, from it, its proper juices; and finally to assimilate it into its own peculiar living substance. I remain, Dear Sir,

Yours faithfully, ANTHONY TODD THOMSON.

91. Sloane Street, 30th November, 1825.

ART. V. On the Life of a Jobbing Gardener. By Mr. ARCHIBALD M'NAUGHTON, of Hackney.

Sir,

Hackney, 29th Nov. 1825. I AM very glad to see your proposal for a Gardener's Magazine, for I have long thought that the gardeners should have an organ to represent them and instruct them, as well as the farmers and mechanics. I have been upwards of fifty

years in the line, and was one of the first who set agoing the London Gardeners' Lodge, described in your Encyclopædia, though I have long since left it, from not being satisfied with its management. I left Edinburgh in the year 1777, and, after working some time in Mr. Christopher Gray's nursery at Fulham, I got a very good place with a Mr. Rolls, a great stockbroker, whose affairs went wrong after I had been six years with him, and I was obliged to quit. After going down to Scotland to see my friends, I came up again and got a place from Mr. Hare, then a seedsman in St. James's Street, to go to Mrs. Wilson at Putney, where I remained till her daughter married, when her husband having an aversion to Scotch servants, I was obliged to leave. Soon after this, a fellow-workman and myself attempted to set up a small nursery at Epsom, part of which is now occupied by Mr. Young of that place; but, after struggling hard for little more than two years, we were obliged to give up, after losing all we had saved, and about 50%, which my partner had borrowed from his aunt at Kinross, and which preyed so upon his mind, that I verily believe it was the cause of his death, which happened about a year afterwards at Windsor; where he got into a small place to look after a garden, and some fields in which vegetables were grown for sale.

Not liking to go into servitude again, I began jobbing on my own account, and a poor business I have found it ever since. When I first began, the highest wages I could get were 3s. a day, and obliged to find my own tools. I had a good deal of employment at first, partly from the circumstance of being a Scotchman, being called by the people who employ jobbers, a professed gardener. My wife also took up a greengrocer's shop about this time, and we did very well till we lost our only daughter, which obliged us to take in a maid-servant, who let in some fellows into the house one Sunday afternoon when we were at chapel, and took away all my savings, most of my wife's clothes, and concealed the bedding in an outhouse, to be taken away no doubt at night. The maid was never seen again, and we never could hear any thing of the thieves. We now left Camberwell altogether, and both my wife and I took a situation in a small family near Hammersmith, where my wife was cook, and I had a man under me for the garden and for looking after a horse and chaise. This place did not suit, and I advertised for another, and got one in a large boarding-school, which was worse, as my wife was expected to look after the milk of two cows, and I was obliged to assist in brewing. After doing nothing for some time, I began the jobbing again at Paddington, and my wife took in washing; but she