of oxygen be detected, but carbonic acid was found in the air in which the plant in the carbonated water was placed, but not a trace in that which surrounded the plant in distilled water. I need not say that these experiments were made in the dark.

There is no reversion of the processes which are necessary to support the life of a plant; the same functions are operating in the same way by day and by night, but differing greatly in degree. During the hours of sunshine, the whole of the carbonic acid absorbed by the leaves, or taken up with water by the roots, is decomposed, all the functions of the plant are excited, the processes of inhalation and of exhalation are quickened, and the plant pours out to the atmosphere streams of pure oxygen, at the same time that it removes a large quantity of deleterious carbonic acid from it. In the shade, the exciting power being lessened, these operations are slower, and in the dark they are very nearly, but certainly not quite suspended.

The experiments of Sennebier show that the most refrangible of the solar rays are the most active in determining the decomposition of carbonic acid by plants. The views of this philosopher have been generally adopted. A few years since, however, Dr. Daubeny published in the Transactions of the Royal Society the results of some experiments which appeared to show that to the luminous or yellow rays, and not to the violet, must this influence be referred; and more recently, at the meeting of the British Association at Cork, Dr. Draper communicated a paper, in which he states that, having tried the effects of the solar spectrum upon tubes filled with water saturated with carbonic acid, and in which leaves were placed, he found that the greatest quantity of gas was set free from the fluid placed in the yellow ray, thus apparently confirming the statement of Dr. Daubeny.

Since this announcement, the very gloomy and uncertain state of the weather has almost entirely prevented my testing the correctness, or otherwise, of Dr. Draper's results. During a few faint gleams of sunshine, I have repeated the experiments in Draper's own method, and have found that bubbles of air have been liberated in the tubes under the influence of the yellow and red rays, but they have been carbonic acid. In the tubes which were placed in the blue and violet rays alone, a perfect decomposition had taken place, and the bubbles which were collected were pure oxygen gas.

Experiments have been made with absorbent media, the light, which has been carefully analyzed, permeating under the influence of the blue light: every instance oxygen gas has been collected, but not any under the energetic action of yellow and red light.

in

However, from the first development of leaves until the perfect maturity of the plant, these processes which we have been considering are continually carried on; and not these only, for it is evident that the same agent is active in producing the decomposition of water, and I believe also of ammonia, from which the plant derives the hydrogen and the nitrogen it requires for the formation of its several principles.

We have now certain knowledge. We know that all the carbon which forms the masses of the magnificent trees of the forests, and of the herbs of fields, has been supplied from the atmosphere, to which it has been given by the functions of animal life, and the necessities of animal existence. Man and the whole of the animal kingdom require, and take from the atmosphere, its oxygen for their support. It is this which maintains the spark of life, and the product of this combustion is carbonic acid, which is thrown off as the waste material, and which deteriorates the air. The vegetable kingdom, however, drinks this noxious air; it appropriates one of the elements of this gas, (car

bon,) and the other (oxygen) is liberated again to perform its services to the animal world. It is not possible to conceive a more perfect, a more beautiful system of harmonious arrangement than this, making the animal and the vegetable kingdoms mutually dependent. The existence of the one ceases when the other is destroyed. If the vegetable world was swept away, animal life would soon become extinct; and if all animal existence was brought to a close, the forest would fall, and the flowers of the field, which now clothe the earth with gladness, perish in the utterness of a lamentable decay. It has been supposed that the vegetable world was called into existence long previous to the creation of animals, and to this period is referred the formation of the coal strata. There might have been an epoch when the disturbed condition of the earth-its earthquake shocks and volcanic strugglings-may have poured so large a quantity of carbonic acid into the atmosphere, as to have rendered this planet unfit for the habitation of animals, until a teeming and most gigantic vegetation, by exhausting it for its own supply, purified the air, and rendered the more quiet earth a fitting abode for creatures endowed with reason and instinct. But such events do not appear again likely to occur, and it is not within the range of probabilities that the animal or vegetable kingdoms will ever have an independent existence.

The animal kingdom is constantly producing carbonic acid, water in the state of vapor, nitrogen, and, in combination with hydrogen, ammonia. The vegetable kingdom continually consumes ammonia, nitrogen, water, and carbonic acid. The one is constantly pouring into the air what the other is as constantly drawing from it, and thus is the equilibrium of the elements maintained.

Plants may be regarded as compounds of carbon vapor, oxygen, hydrogen, and nitrogen gases, consolidated by the all-powerful, all-pervading influences of the solar ray; and all these elements are the produce of the living animal, the condition of whose existence is also greatly under the influence of those beams, which are poured in unceasing flow from the centre of our system. Can any thing more completely display a system of the loftiest design and most perfect order than these phenomena ?

The most casual observer could not fail to remark the peculiar influences of the solar agencies at different seasons of the year. In spring, a fresh and lively green pervades the field and forest; this in summer assumes a darker hue, and in the autumn passes gradually into a russet brown. In a very early stage of my photographic researches, I discovered a remarkable difference in the chemical action exerted by the solar rays an hour or two before noon, or an hour or two after it. I am now convinced-although it will require continued observation for many years to prove it-that the same difference is to be detected between the solar emanations of the vernal and the autumnal periods. The change in the color of the leaves appears to be entirely dependent upon the absorption of oxygen, which all the green parts of plants have the power of absorbing, particularly in the dark. This true cause of chemical affinity, it would appear, goes on equally with the spring or the summer leaves; but during these periods the vital force, under the stimulus of the light, is exerted in producing the assimilation of the oxygen for the formation of the volatile oils, the resins, and the acids. In the autumn this exciting power is weakened; the summer sun has brought the plant to a certain state, and it has no longer the vital energy necessary for continuing these processes. Consequently, the oxygen now acts in the same manner on the living plants as we find in experiment it acts upon the dried green leaves, when moistened and exposed to its action. They absorb gas and change color.

HOW PROTECTION AFFECTS THE FARMERS OF GERMANY. 679

Sir John Herschel observes, in reference to the action of light on the juices of plants: "The earlier flowers of any given species reared in the open air, are more sensitive than those produced, even from the same plant, at a late period in its flowering, and have their colors more completely discharged by light. As the end of the flowering period comes on, not only the destruction of the color by light is slower, but residual tints are left, which resist obstinately." These residual tints are the same which produce the brown of the autumnal leaf; and the same agent may be traced in the production of photographs upon papers spread with expressed juices, and on the changing colors of flowers and of leaves.

A remarkable example of the influence of light upon the juice of plants, is seen in the Cacalia ficoides, cited by Liebig. During the hours of darkness, this plant, like others, absorbs oxygen, and in the morning it is as acid to the taste as the sorrel. By the influence of the morning sun it loses this oxygen; at noon it is tasteless; and, by the continued action of the light, still more is abstracted, and the plant is positively bitter in the evening.

Experiments have been instituted with a view of ascertaining if any particular ray of the spectrum had the power of inducing, more powerfully than others, the progress of plants towards the light, a phenomenon which is strikingly exhibited by the potato. It would appear that the yellow or pure luminous rays exert this influence with the greatest force; but it must be admitted that the results obtained have not been so satisfactory as could be desired. Indeed, no correct conclusion can be arrived at, until the experiments are tried with the isolated rays of the prismatic spectrum themselves. I am every day more and more convinced of the defects of absorbent media in these and similar researches.

HOW PROTECTION AFFECTS THE FARMERS OF GERMANY.

A FEW months since, we laid before our readers a statement respecting the sugar trade of France, showing that, although that made from the beet enjoyed no protection whatsoever, it was gradually driving out the colonial sugar, the advantages resulting from proximity to market more than counterbalancing those resulting from the tropical climate of the sugar islands. We now have to record the still more remarkable growth of the culture of sugar in the States of the German Zoll-Verein.

The table before us gives only the quantity of beet-root cultivated; but the general estimate thoughout Germany is that, with the greatly improved processes resulting from a few years of protection, they now obtain one part of sugar from twelve of beet; and we have, therefore, added another column, giving the quantity of sugar in centimes, and a third, in which is given, in round numbers, the amount of the latter in tons, as follows:

We have here the most remarkable growth of agricultural production that

is, as we believe, on record; and it occurs precisely as the loom and the spindle, the hammer and the anvil, are, more and more, taking their natural places by the side of the plough and the harrow, as is seen in Belgium, and Germany, and Russia; while throughout the world, the tendency towards the diminution of production exists in the precise ratio of subjugation to the unnatural system attempted to be established by England, as witness, Ireland, Portugal, Spain, Turkey, India, and all other of the colonial possessions of Great Britain.

ON THE ADVANTAGE OF THICK SOWING.

BY DAVID BARCLAY, M.P.*

THE following is the result of some experiments which I made last year, in order to ascertain the relative merits of thin and thick sowing wheat, drilling, dibbling, and by broad-cast. They were conducted with great care upon five acres of level land of uniform quality, being a good deep loam on a chalk subsoil, following a clover ley folded by sheep. The land was ploughed about five inches deep, as it was not thought desirable to bury the sheepdressing below that depth. The seed was put into the ground about the 7th of December, 1843, and the wheat was hoed in the spring of 1844, except the acre sown by broad-cast, which was harrowed instead of being hoed. The plants in Nos. 2 and 3 (thin sowings) were by much the strongest, and looked the best throughout the season, until the approach of harvest, when it became evident that the quality of the grain and straw was inferior, more particularly on No. 2, which appeared to have suffered a little from mildew. Samples of the different lots were submitted to an eminent miller, and the value of each determined by him; the straw was valued at the market price. (See next page.)

The results of these experiments are very remarkably in favor of thick sowing, and particularly of the old broad-cast system; and if not conclusive against the doctrine of thin sowing, so strongly, and, I may add, so ably advocated in the present day, should at least induce caution on the part of farmers before they depart from the practice of their forefathers. Indeed, it is difficult to believe that so great an advantage as the saving of a bushel or a bushel and a half of seed per acre can have been overlooked for so many generations. It seems more reasonable to suppose that long practical experience has taught the farmer the more prudent course of a liberal supply of seed. It may however be contended, that had the ploughing been deeper and the seed put earlier into the ground, the result would have been different: this is not improbable; and it is possible the deficiencies in the quality and quantity of thin-sown wheat and straw might have been less observable, but the large differences which my experiment indicates could hardly, I think, have been made up. I have this year repeated the trial of thin sowing, having drilled one acre on the 26th of October last (the land having been deeply ploughed) with one bushel of seed, the rest of the field having two bushels per acre. The result I shall be happy to communicate if desired.

* Journal of the Royal Agricultural Society, London.

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