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ticles which are endued with life, Mr. K. conjectures, that the same fluid, by acquiring different motions, may generate different organs than that two distinct fluids should be necessary to form the root, and the bud and leaf. When alburnum is formed in the root, that organ possesses, in common with the stem and branches, the power of producing buds and of emitting fibrous roots; and when it is detached from the tree, the buds always spring near its upper end, and the roots near the opposite extremity. The alburnum of the root is also similar to that of other parts of the tree, except that it is more porous, probably owing to the presence of abundant moisture during the period in which it is deposited. Perhaps the same cause may retain the wood of the root permanently in the state of alburnum; for if the mould be taken away, so that the parts of the larger roots which adjoin the trunk be exposed to the air, such parts are subsequently found to contain much heart wood.

In opposition to the opinion, that fibrous, like bulbous roots, of all plants, are only of annual duration, it is observed that, with regard to the latter, nature has provided a distinct reservoir for the sap, which is to form the first leaves and fibrous roots of the succeeding season; but the organisation of trees is different, and the alburnum and bark of the roots and steins of these are the reservoirs of their sap during winter. When, however, the fibrous roots of trees are crowded together in a garden-pot, they are often found lifeless in the succeeding spring; but this mortality does not occur in the roots of trees when growing under favourable circumstances in their natural situation.

Experiments on the most advantageous Method of constructing Voltaic Apparatus. By Mr. JOHN GEORGE CHILDREN. His battery consisted of upwards of 92,000 square inches in surface, each plate being four feet by two; and it was charged with a mixture of three parts of fuming nitrous, and one part of sulphuric acid, diluted with 30 parts of water With this battery he fused completely 18 inches of platina wire,th of an inch in diameter, in 20 seconds, and 10 inches of iron wire, th of an inch thick: charcoal was burnt, giving out an intense brilliancy. But on imperfect conductors it had not the slightest effect; and on the human body it was hardly perceptible; and it had scarcely any effect on the gold leaves of an electrometer.

But with a second battery, consisting of 200 pair of plates,

each about two inches square, placed in half-pint pots of common queen's-ware, and rendered active by some of the liquor used in exciting the large battery, to which was added a small portion of fresh sulphuric acid, he readily decomposed potash and barytes: in that state it produced the metallisation of ammonia with great facility; it ignited charcoal vividly; it caused great divergence in the leaves of an electrometer; and it gave a vivid spark after being in action three hours.

Hints on the Subject of Animal Secretions, with a View of throwing new Lights on Animal Chemistry. By Mr. EVERARD HOME.[1810.]

THE discoveries of Mr. Davy suggested to Mr. Home the idea, that the animal secretions may be produced by chemical changes effected by the power of electricity.

The voltaic battery, he observes, is met with in the torpedo and electrical eel, a circumstance that furnishes two important facts: one, that a voltaic battery can be formed in a living animal; the other, that nerves are essentially necessary for its management; for in these fish, the nerves connected with the electrical organs exceed those that go to all the other parts of the fish, in the proportion of twenty to one. The nerves

are made up of an infinite number of small fibres, a structure so different from that of the electric organ, that they are evidently not fitted to form a voltaic battery of high power: but their structure appears to adapt them to receive and preserve a small electrical power. That the nerves arranged with muscles, so as to form a voltaic battery, have a power of accumulating and communicating electricity, is proved by the well-known experiments on the frog.

The

There are several circumstances in the structure of the nerves, and their arrangements in animal bodies, which do not appear at all applicable to the purposes of common sensation, and whose uses have not even been devised. organs of secretion are principally made up of arteries and veins; but there is nothing in the different modes in which these vessels ramify, that can in any way account for the changes in the blood, out of which the secretions arise. These organs are also abundantly supplied with nerves.

By experiments, it was ascertained, that a low negative power of electricity separates from the serum of the blood an alkaline solution of albumen; that a low positive power separates albumen with acid, and the salts of the blood; that with one degree of power, albumen is separated in a solid,

form-with a less degree, it is separated in a fluid form. From these facts the following queries are proposed: 1. That such a decomposition of the blood, by electricity, may be as near an approach to secretion as could be expected to be produced by artificial means, at present in our power. 2. That a weaker power of electricity than any that can be kept up by art, may be capable of separating from the blood the different parts of which it is composed, and forming new combinations of the parts so separated. 3. That the structure of the nerves may fit them to have a low electrical power; and as low powers are not influenced by imperfect conductors, as animal fluids, the nerves will not be robbed of their electricity by the surrounding parts. 4. That the discovery of an electrical power which can separate albumen from the blood in a fluid state, and another that separates it in a solid state, may explain the mode in which different animal solids and fluids may be produced, since albumen is the principal material of which animal bodies are composed. 5. That the nerves of the torpedo may not only keep the electric organ under the command of the will, but charge the battery, by secreting the fluid between the plates, that is necessary for its activity. 6. As albumen becomes coagulated by the effect of a power too low to affect the most delicate electrometer, may it not occasionally be employed as a chemical test of electricity, while the production of acid and alkali, affected by still inferior degrees of electricity to those required for the coagulation of albumen, may likewise be regarded as auxiliary tests on such occasions?

On the Duration of Voluntary Action; on the Origin of Sea Sickness; and on the Advantage derived from riding, and other Modes of Gestation, in assisting the Health under various Circumstances. By Dr. WOLLASTON.

IN speaking of the duration of muscular power, he observes, that each effort, though apparently single, consists in reality of a number of contractions repeated at extremely short intervals, so short that the intermediate relaxations cannot be visible, unless prolonged beyond the usual limits by a state of partial or general debility. The existence of these alternate motions he infers from a sensation perceptible upon inserting the extremity of the finger into the ear, because a sound is then perceived which resembles that of carriages at a distance passing rapidly over a pavement, and their frequency he estimates at twenty or thirty in a second.

The doctor was led to the investigation of the cause of sea-sickness from what he himself experienced in a voyage. He first observed a peculiarity in his mode of respiration, evidently connected with the motion of the vessel. The principal uneasiness is felt during the subsidence of the vessel by the sinking of the wave on which it rests. It is during this subsidence that the blood has a tendency to press with unusual force upon the brain. This fact is elucidated by reasoning, and by what is known to occur in the barometer, which, when carried out to sea in a calm, rests at the same height at which it would stand on the shore; but when the ship falls by the subsidence of the wave, the mercury is seen apparently to rise in the tube that contains it, because a portion of its gravity is then employed in occasioning its descent along with the vessel; and accordingly, if it were confined in a tube closed at bottom, it would no longer press with its whole weight upon the lower end. In the same manner, and for the same reason, the blood no longer presses downwards with its whole weight, and will be driven upwards by the elasticity which before was merely sufficient to support it. The sickness occasioned by swinging may be explained in the same way. It is in descending forwards that this sensation is perceived, for then the blood has the greatest tendency to move from the feet towards the head, since the line joining them is in the direction of the motion; but when the descent is backwards, and the motion is transverse to the line of the body, it occasions little inconvenience, because the tendency to propel the blood towards the head is inconsiderable. Dr. Wollaston thinks that the contents of the intestines are also affected by the same cause as the blood; and if these have any direct disposition to regurgitate, this consequence will be in no degree counteracted by the process of respiration. "In thus referring," says our author, "the sensations of seasickness in so great a degree to the agency of mere mechanical pressure, I feel confirmed, by considering the consequence of an opposite motion, which, by too quickly withdrawing blood from the head, occasions a tendency to faint, or that approach to fainting which amounts to a momentary giddiness with a diminution of muscular power.

His explanation of the effects of external motion upon the circulation of the blood is founded upon a part of the struc ture observable in the venous system. The valves allow a free passage to the blood, when propelled forward by any motion that assists its progress; but they oppose an immediate obstacle to such as have a contrary tendency. The circulation

is consequently helped forward by every degree of gentle agitation. The heart is supported in any laborious effort; it is assisted in the great work of restoring a system, which has recently struggled with some violent attack; or it is allowed as it were to rest from a labour to which it is unequal, when the powers of life are nearly exhausted by any lingering disorder. In the relief thus afforded to an organ so essential to life, all other vital functions must necessarily participate, and the offices of secretion and assimilation will be promoted during such comparative repose from laborious exertion.

On the Old Age and Decay of Trees, By Mr. KNIGHT.

THE roots of trees, particularly those in coppices which are felled at stated periods, continue so long to produce and feed a succession of branches, that no experiments were required to prove, that it is not any defective action of the root which occasions the debility and diseases of old varieties of the apple and pear-tree. Having formerly adduced arguments, which are uncontradicted, to show that the sap of plants circulates through their leaves as the blood of animals circulates through their lungs; and having also shown that grafted trees of old and debilitated varieties of fruit became most diseased in rich soils, and when grafted on stocks of the most vigorous growth, which led him to suspect that in such cases more food is collected and carried up into the plant than its leaves can prepare and assimilate; and the matter thus collected, which would have promoted the health and growth in a vigorous variety, accumulates and generates disease in the extremities of the branches and annual shoots, while the lower part of the trunk and roots remain generally free from any apparent disease; he hence attributes the diseases and debility of old age in trees to an inability to produce leaves which can efficiently execute their natural office, and to some consequent imperfection in the circulating fluid. It is said, that the leaves are annually reproduced, and are therefore annually new; but there seems to be an essential difference between the new leaves of an old and of a young variety; and it is certain, that the external character of the leaf of the same variety at two, and at twenty, years old, is very dissimilar; and therefore to Mr. Knight it appears not improbable, that further changes will have taken place at the end of two centuries. "If," says he, "these opinions be well founded, and the leaves of trees be analogous to the lungs of animals, is it improbable that the

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