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ELECTRO-VEGETATION.:

54 periments the conclusion that the change produced by the vital action of the vegetable, excited by solar light, is the decomposition of carbonic acid, and consequent evolution of oxygen." Heat, in the absence of light, is known to be wholly inefficient in the production of this process. We have, then, in this case, an evidence of several chemical effects to which light, as distinguished from heat, is essential;-the decomposition of carbonic acid, attended probably with a deposition of the carbon in the leaf, or its union with some other substance contained in it, (and the extraction of its oxygen, which probably, by entering into combination with the particles of light, escapes in the form of gas. Is it not reasonable to conclude, that the agent in the produc ́tion of these chemical changes is identified with the electric fluid; and that thus the solar beams, instead of accumulating in the atmosphere in the form of electricity, and generating storms or hurricanes, are converted into the means of maintaining the vital principle in animals? By this means one portion of that fluid, which is so copiously dispensed from the sun in the summer season, may be conceived as being both neutralized, or prevented from proving the occasion of much disorder and injury in the system of nature,-and converted into the great essential of animal vitality; while a much larger portion is neutralized by a similar combination with the particles of water, and by forming clouds and rain, both mitigates the heat, and again imparts nurture to vegetation.

These rays, if suffered to float in the atmosphere without entering into these combinations, would either derange the harmony of nature by electrical concussions far exceeding any which fall under our experience, or by rarifying and raising the temperature of the atmosphere in the like unexampled and intolerable degrees, render it in these respects, as well as by the probable absence of oxygen, unfit for the purposes of animal existence.

The following experiment will serve to show the necessary presence of carbonic acid in an atmosphere of water to the production of oxygen gas. Some water, out of which the air had been boiled exhibited no gas from a sprig of vineleaves exposed to the sun's rays; but on being impregnated with carbonic acid, and placed in the same circumstances,

large and copious globules appeared on the back of the leaves; and on burning a taper in the gas collected from them, the light was extremely brilliant, This experiment has been repeated in the presence of several persons who were fully satisfied with the result. By many trials I also find that in proportion as the oxygen gas is produced, rhe carbonic acid disappears from the water, and indeed that it is withdrawn from it by the action of the leaves in the absence of light, and during the night season, though no oxygen is produced but on exposure to the solar rays. Having placed a fresh leaf in some pump water which I had found to yield globules to fresh leaves freely when exposed to light, and excluded the light from them for about an hour, I was surprised to observe that on removing the covering, and suffering the leaf and water which had been in darkness to remain a considerable time under the beams of the sun, no globules whatever appeared; and from subsequent observations on sprigs of leaves in jars of the same water, I discovered that the carbonic acid was as completely removed by the action of the leaves, though remaining in total darkness, as if it had been expelled by boiling; no globules appearing in the jars of water which had been confined with sprigs of vine-leaves for about ten hours, provided those leaves were removed and fresh leaves were introduced: whereas when the same leaves remained in it, which, on being wetted by lime water, remained transparent, they, after having been exposed a few hours to the light, began to yield globules; showing that having imbibed the carbonic acid while in darkness, they now yielded its oxygen from the pores under the action of light.

That solar light extracts oxygen from "the leaves of plants, their green shoots or branches, or even the entire vegetable under water," was the observation of Ingenhouz; and he found also that "its production was considerably dependant on the nature of the water under which the vegetable was immersed. It has been since shown by the experiments of Sennibier, Woodhouse, and Saussure, that it is much connected with the presence of carbonic acid; so that in water entirely free from this, the evolution of oxygen gas is very inconsiderable, while in water impregnated with it it is abundant. It may be inferred, therefore, that it is

ELECTRO-VEGETATION.

principally from the decomposition of the carbonic acid by the pores of the plant, aided by the agency of the light, that the oxygen is evolved."* Here are strong confirmations of the principal facts which I have adduced, excepting that these distinguished philosophers appear to have been of opinion that a small portion of the oxygen might proceed from the plant itself in a more direct manner; and that they make no mention of the action of the leaves, by imbibing the carbonic acid in the absence of light. As this particular, being new and wholly unanticipated by me, strongly attracted my attention, I repeated my observations with care, and can entertain no doubt whatever of the fact. I cannot help regarding it as a very satisfactory evidence of the useful operation of plants during the night season, if we admit that they exercise the same function of attaching carbonic acid to their substance under their ordinary circumstances surrounded by air, which they manifest when immersed in water. That they do exercise this function in air, appears from the experiments of Davy and Woodhouse, above alluded to; and as it is probable that a function which appears to be natural to them is exerted with the greatest perfection in their proper element, it seems reasonable to conclude that they are very operative in removing from the atmosphere the deleterious gas which is exhaled from the lungs of animals, by night as well as by day, although they are indebted to the assistance of solar light in evolving the oxygen from the carbon, which now enters permanently into their substance.

Mr. Weekes informs me, as one of the results of his experiments with his new pneumatic apparatus, that healthy plants do yield carbonic acid occasionally, but not in sufficient quantities to affect the conclusion that oxygen gas is their general aerial produce. It has been the opinion of some physiologists that they absorb oxygen, and give out carbonic acid during night. I admit that the oxygen which has been given out during the day sustains some diminution in the night, when the experiment is made over water with the leaves imerged in it; but this is probably to be ascribed to the absorption of the water. It evidently requires a due regard to proportions in introducing

See Murray's Chemistry, vol. ii. p. 288, &c.

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carbonic acid to the action of plants, From one of my experiments, it appeared that two vine-sprigs, each with several leaves in a jar of water from which the air had been withdrawn by the previous action of leaves in it, became beautifully illumined with globules of oxygen, by introducing about one-fourth of its bulk of carbonic acid into the water. Hence it is probable that a very small proportion of this gas diffused through the air is best suited to the absorbent property of the plants; and perhaps that minute proportion in which it is ordinarily found in the atmosphere, is that which is best suited for their action in that element. Priestley found that when mixed with it in the proportions of from one-half to one-eighth, the plant confined in this mixed atmosphere was almost instantly destroyed; and I have found the leaves apparently injured by too large propor tions of the gas in water, under which cireumstances it is highly probable that they occasionally give out a portion of it unaltered, especially when kept beyond their natural or ordinary time in darkness. The results, however, which have fallen under my observation are such as I have above stated; the leaves appearing to attract the carbonic acid from the surrounding medium at all hours, in darkness as well as in the light, and yielding its oxygen under the influence of the solar

rays.

One inference follows from the fact, that the production of oxygen gas from the leaves of plants depends on the presence of carbonic acid in the surrounding medium, which I would hope may prove of some practical utility. Carbonic acid can be procured with considerably more facility than oxygen gas in the ordinary methods; but by impregnating water, containing branches of leaves exposed to the solar rays, with the former of these gases, the latter might be obtained in quantities sufficient for several purposes; as for the recovery of suspended animation in the cases of still-born children, of drowning or other medicinal uses, by being kept in glass bottles well sealed. At any rate, an attention to the requisite quan.ity of the aerial acid in the water in which vegetables are immersed in order to obtain oxygen gas from them will greatly facilitate success, without which the mere addition of fresh leaves to the water would prove almost wholly un

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KIRKBY SLATE QUARRIES.

availing; whereas their under surfaces will speedily become finely bedecked with large globules of oxygen, when the water has been impregnated with about one fourth of its bulk of carbonic acid. It will probably occur to the recollection of some of your readers, that "the lady of a physician having a child still-born, all the common means were tried without effect. Recollecting he had a bladder of vital air, with which he was about to make an experiment, the doctor forced this air into the lungs of the infant, when the eddies of its little heart began to play, and the child was restored." Mr. Weekes informed me, that "he had several times actually used oxygen in cases of suspended animation, and with success; and that in the last instance, he had recovered a boy, who was then living four years after, when he had been twenty minutes under water. I find," he adds, "the best method, because the simplest, is to pass an elastic tube into the windpipe, and then inflate the lungs by having the gas diluted with one-third atmospheric air, in bladders ready to attach to the pipe." I have ventured to trespass from the proper object of this paper with these remarks on the means of obtaining oxygen, and this important practical application of the gas, particularly by my friend, in the hope of their conducing to some future usefulness-wishing to obtain all the light and information in my power upon the subject of the electric relations of the soil to vegetation, and the influences of the solar fluid in its connexion with it. I must here close this letter.

I remain, Sir,
Yours respectfully,

T. PINE.

dipping to the south: and that fig. 2 represents the section of a back, also on a vertical north and south plane, ab, being here also the direction of the cleavage dipping to the south.

Now it will be manifest that if fig. 2 be put into the position of fig. 1 the lines indicating the cleavage in each, will dip in contrary directions:-and supposing a change had taken place in the position of the rock, I could then only account for the dip of the cleavage in both back and feet being to the south, by supposing that one had actually turned round in the manner I have described, and which I may further illustrate by stating that if fig. 2 be drawn on the other side of the same paper on which fig. 1 is placed, and that both figs. 1 and 2 be then examined by looking through the paper, the dip of the clevage, (the plane of stripes being in the same direction) will then be in the same direction in both.

Figs. 1 and 2.

KIRKBY SLATE QUARRIES.

Sir,—In a former paper on this subject, amongst other circumstances I endeavoured to describe the distinctions between what are called back and foot quarries; and at that time supposing the plane ofcleavage to have some determinate angle with respect to the plane of the stripes, I described the peculiar motion that must have taken place to change the one into the position of the other; I had observed for example, that fig. 1 represents the section of a foot on a vertical north and south plane, and ab the direction of the plane of cleavage in that foot

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These appearances had been observed in so many extensive quarries, and both near and at such distances from each other as to have fixed the terms backs and feet, as the means by which those engaged in or about the quarries distinguished the position of the rock in quarries which differed from each other. I had notwithstanding noticed that the angle which the cleavage makes with the stripes was more oblique in the backs than in the feet, but this was not sufficient to lead me to expect so extraordinary a fact as the following.

KIRKBY SLATE QUARRIES."

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lafer-boarding, or in ship building clinker built. When in this state the rock became united and hardened.

The direction of the cleavage in some of the feet just alluded to is a little changed, although the general cleavage of a large block may be very nearly a plane, yet at every stripe a slight deviation takes place, forming a ridge. The material of the stripes is not only of a finer texture, but it is something harder than the other parts of the slate rock.

The cleavage is also in some places altered by the nodules, and the occurrence of other harder or different material by which a carved and uneven surface is produced. The largest nodules that have been observed, are 2 feet long, 16 inches

Fig. 4.

b

ab's being the direction of the cleavage, and all parallel or nearly parallel to each other, dipping to the south; and, indeed, as well as in all other quarries which have been observed, with a bearing very nearly magnetic, east and west. It therefore appears clearly from this, that the cleavage can be in no way regulated by what appears to have been originally the strata of the slate rock material, as indicated by the stripes, and the great joints parallel thereto. Since this was observed, indications in other quarries have been perceived, from which it may be inferred that a like connection between the feet and the backs may ultimately be traced.

From these and other appearances, perhaps it may be inferred that the slate rock material was once in a plastic state, and that the property of cleavage occurred subsequently to the period when the mass obtained the position in which it is now found.

In some of the feet an appearance has been observed as if the material in the plane of the stripes had moved while in a plastic or disunited state. This will perhaps be better understood by supposing a number of quires of paper, say, alternately a quire of plain and a quire of gilt edged-and the gilt or plain having moved, they project one before the other, not unlike what in building is called

Fig. 5.

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KIRKBY SLATE QUARRIEST

broad, and 9 thick, with an appearance similar to the sketches, figs. 4 and 5; the transverse section being oval. The nodules are striped like the ordinary slate material in which they are found embeded; but they are either much harder than the slate, or otherwise they are as soft, and not unlike generally brown rotton stone. Indeed, one of the large nodules alluded to was partly sound and partly rotten. There is no reason, however, to suppose that the hard parts would, by exposure to the atmosphere for any known length of time, become soft.

Side Seams.

Besides the joints which are parrallel to the stripes, there are others which cross them. The greatest of these are called side seams, the bearing of which is nearly north and south, and the dip at a very considerable angle to the east. Whereever a side seam has been discovered, it has been found to extend through all the feet or backs as far as the quarries have been wrought; so the extent of these joints is not known, These joints have been observed to have nearly the same direction in both back and feet quarries. The distance they are apart in some places is not more than 20 feet, while in others, they are much more, and in some extensive quarries no side seams have yet been discerned. Some side seams are nearly planes, others differ from them in degree of roughness and irregularity, as well as in the material in the joints. It has been remarked by the workmen that when the side seams are the nearest to a plane, the cleavage also presents the evenest surface. This is remarkable as the plane of cleavage crosses the plane of the side seams.

Ends.

Each foot and back, or whatever other position the stripes or strata of the rock may have, are crossed by seams or joints called ends, the bearing of which is nearly north and south, or the same as the side seams, but the dip is generally nearer vertical. In some feet and backs the end joints are very close to each other; but in those which produce the largest material, they are at a much greater distance. One part of the same foot or back frequently contains more of these end joints than are found in an equal portion of another part. These end joints in a foot or back not only do not continue through

into the adjoining feet or backs, but frequently they only extend a little distance into the rock forming the foot or back, when they terminate. Some of these joints are by the workmen called sawgates, and indeed they very much resemble the cut made by a saw in any material; the sides of the joints being parallel, and terminating as abruptly in the solid material as a saw-kerf in a plank, block of wood, or any other substance. Sometimes these joints are so close as not to be perceptible, and when they terminate, the workmen say the rock is grown together.

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These are nearly vertical, and their bearing varies from nearly north and south to north-east and south-west. These cross the direction of all the joints, and divide the slate back. Several of these have been observed at about 100 feet distance from each other.

One of these veins, which has been more particularly noticed, is about two feet thick; and the corresponding feet on the east side are between two and three feet lower than those on the west side of the vein. Thus, either the rock has been raised on one side of the vein, or on the other side it has sunk.

From the constant observation of the workmen, they find that the slate-rock, if not rendered quite useless, or poisoned, as they term it, by being near these ram

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