CHAP. XVII.The influence of electricity on vegetables.
With regard to this part of our subject there has been considerable controversy between philosophers, some of them asserting that electricity is unfavourable, and others that it is advantageous to vegetation. It was asserted by the Abbè Bertholon, in his book entitledElectricitè des meteores, that plants situated near a metallic conductor increased considerably in consequence of their situation. And, on the other hand, Giardini says that plants growing near such conductors are generally unhealthy, and produce very little fruit, but upon removing the conductor the plants become luxuriant and fruitful.
The Abbè Bertholon in endeavouring to establish his opinion, constructed what he called anelectro vegetometerby means of which the electricity of the atmosphere may be collected in abundance. “This apparatus (says he) having been raised with care in the midst of a garden, the happiest effects were perceived, viz. different plants, herbs and fruits, in greater forwardness than usual, more multiplied and of better quality.” These facts are analogous to an observation that I have often made, viz. that plants grow best, and are more vigorous near thunder rods, where their situation favours their developement. They likewise serve to explain why vegetation is so vigorous in lofty forests, and where the trees raise their heads far from the surface of the earth, so that they seek as it were the electric fluid at a far greater height than plants less elevated: while the sharp extremity of their leaves, boughs and branchesserve as so may points granted them, by the munificent hand of nature, to draw down from the atmosphere that electric fluid which is so powerful an agent in forwarding vegetation, and in promoting the different functions of plants.—Such are the theory and experiments of the Abbè, but Doctor Ingenhaus, in two letters to Mr. Molitor, published in thejournal de physiquefor 1786–88 has shewn the fallacy of the theory, by exposing the insufficiency of the experiments upon which it was established.
We shall translate a few passages from the Doctor’s letter, which will shew us his opinion and the result of his experiments.
I have frequently made experiments of this kind by exposing plants to a weak degree of electricity, and at other times to a considerable quantity, without ever being able to observe that plants under its influence prospered more than those which were not electrified at all. It even appeared to me more than once, that those which had been electrified were a little less thrifty than those which were not electrified.
In another place he says, Not being content with these experiments, I have made others infinitely more conclusive, by strewing seeds of mustard and cresses, over the largest plates of delf that I could procure, covering them with brown paper, and sprinkling them continually with a sufficiency of water. Each of these plates was covered with more than a thousand seeds; I kept them electrified night and day, according to the method which Mr. Schewankhard directed, in a letter quoted by Mr. Elermann, but which I shall not repeat in this place, lest I should swell this memoir: the vegetation of these little shrubberies was always more orless precarious, in proportion to the greater or less quantity of light that they received; the electricity really contributing nothing to advance the growth: thus the controversy stands, we leave the reader to form his own opinion.
That some plants are more affected than others by electricity is an unquestionable fact. It is however not true as some have affirmed, that the contractions of the mimosa or sensitive plant, are attributable to this cause. The plant is equally affected when touched either by a conductor or an electric.
Electricity has one advantage over other medical applications, in as much as it may be applied to the healthy, as well as the diseased part of the body, without proving prejudicial, and because it requires rather a nice application, than a perfect knowledge of the complaint. In a number of cases it has unquestionably proved salutary.
When electricity was first used in removing bodily complaints, it was done only by means of the Leyden phial pretty highly charged; but this mode of administering it, was strenuously opposed by Mr. Lovet, who was a celebrated electrical practitioner, and in an essay calledSubtil medium proved, asserts that electricity should be used in small sparks, by which mode of treatment he affirms he scarcely ever failed curing or at least relieving his patients.
The apparatus for medical electricity in addition to the machine described in chapter IV, is aninsulating stool. This stool is made in the common way, only that the feet must be of glass, the upper or wooden part, should be about three feet square, so that a chair or bench may conveniently stand upon it; care must be taken to leave no sharp edges about the stool. For a representation of one, see plate letter W.
The next instrument necessary for the electrical physician is a coated jar, furnished with Mr. Lane’s electrometer. This instrument is made in the following manner. From the wire extending beyond the mouth of the jar, at about four inches from the upper extremity, let a piece of glass or baked wood three inches long, project at right angles. At the outer extremity of this stem let another piece of baked wood three inches long, be fixed parallel to the rod of the jar; the upper end of the parallel stem must be furnished with a brass socket, through which a graduated wire may easily pass. This wire must be furnished with a knob upon the end which is next the jar, and a hook or ring at its other extremity, to which a chain connected with the outer coating of the jar must be attached. From this construction it is readily perceived that the force of the discharge or shock, will be proportioned to the distance of the ball of the electrometer, and the usual ball of the jar; i. e. when the shock is large it will pass from one knob to the other at a larger distance, and when small at a smaller distance, and thus the distance will be the measure of the shock.—The next thing to be provided is a ball, either of metal, or of wood covered with tin foil; this must have a metallic handle, which may be separatedfrom the ball at pleasure, having at one of its extremities a sharp point to receive a stream of electric fire; small pointed pieces of wood made in a conical shape, may be fixed on this point, when the patient requires a degree of electricity between a spark and a stream.
The bottle director is the next instrument to be described. It is exactly the same with the common Leyden phial, with the addition only of a hook cemented to the bottom. To use this director (suppose for instance you wished to pass a shock through the arm) let a communication be made between its inner coating and the prime-conductor, by which means it will be charged; then let a chain be fastened, by one end, to the hook which is at the bottom; then by applying the other end of the chain (which may be furnished with a ball) to one side of the arm, and the knob of the jar to the other, a shock will be given.
These are the instruments for the electrical physician. We are now to describe the manner in which electricity may be applied to the best advantage.
1st. By simply placing the patient upon the electrical stool. While the machine is in action the patient constantly emits the overplus of the electric fluid that he receives, which continually passes off from every part of his body, and produces a salutary effect. It may be suspected that so gentle a treatment could have but little influence. It is however upon good authority we assert, that nervous and sedentary persons have derived considerable advantage from this mode of application.
2d. By electric friction. Let the part affected be covered with a piece of flannel or woollen cloth, and placethe patient upon the insulated chair, and connect him with the prime-conductor; then take a metallic ball, communicating with the earth, and rub it over the flannel or woollen cloth. Electricity thus applied has often removed violent spasms, and many other afflicting complaints.
3d. By drawing sparks. Let the patient, as in the last instance, be placed upon the insulated stool, and connected with the prime-conductor; then bring the metallic ball, communicating with the ground, within about half an inch of the part affected, and sparks will pass from it to the ball. Cutaneous eruptions, scrophulous tumours and deafness, are frequently benefitted, and sometimes removed, by this method of application. Deafness, in particular, has been entirely cured by the electric spark, when every other remedy has proved ineffectual. One of these cases came under our own observation. A gentleman who was affected with an almost total loss of hearing for more than six months, was advised by his physician to make a trial of electricity as a remedy. He applied to us, and was under our care about four or five weeks, when he left us almost entirely recovered. This gentleman was treated in the following manner.
We placed him on an insulated chair communicating with the prime-conductor. Then, with a blunt pointed wire inserted into a glass tube, we drew sparks from themeatus auditorius. This operation was continued for eight or ten minutes, at every visit. He commonly attended us twice or thrice a week. We were fully persuaded that the cure would have been more speedy, if he had received the electricity more frequently.
4th. By the stream. Place the patient as in the two last instances; then bring the point, instead of the ball, near the part affected. When the electrical stream is to be applied the wooden point is preferable to the metallic one. Inflammations and other diseases of the eyes, and several other disorders, have been thus removed.
5th. By the director. Place the patient on a chair—insulation in this case being unnecessary. Then lay the ball, which communicates with the outside coating of the director, upon the affected part; after which, bring the director, which must have been previously charged, near any other part of the body, and the intended operation will be performed. It is impossible to tell the precise quantity of electricity which ought to be administered in every complaint, because persons who are affected with the same disease will sometimes require very different degrees of electrization, which must be judged of by the nature of their constitution, their habits of body, and other circumstances. Small sparks will sometimes have more effect upon a delicate and irritable constitution, than pretty powerful shocks upon others. The Leyden phial, with Mr. Lane’s electrometer, is the most convenient instrument for sending shocks of different powers through particular parts of the body.—To use this.—Let the wire of the electrometer be placed at the proper distance for the required shock; connect a chain or wire, communicating with this, with the part affected—and let a communication be made between any other part of the body and the outside coating of the phial. Now turn the cylinder, and the phial, when it has received the proper charge, will discharge itself through the circuit formed by the chains or wires, andthe part of the patient which was to be subjected to the shock.
The machine described in Chapter IV, or one similar to it, is capable of exhibiting the principal electrical phenomena, provided it be skilfully managed; but without such management it will constantly disappoint the electrician, and prove of little use. Let the following directions and observations, then, be attentively regarded.
1. Keep all the instruments as free as possible from dust and moisture.
2. When the weather is clear, the air dry and a little cold, the electric fire may be easily and copiously collected. But when the weather is hot or damp, the electrical machine is much less powerful.
3. Before the machine is used, the cylinder should be wiped clean, with a linen cloth that is soft, dry, and warm; after which a clean hot piece of flannel, or old silk handkerchief, may be applied with advantage.—This done, if the cylinder be turned pretty fast, when the prime conductor and other instruments are removed, the electricity, upon applying the knuckle or other conductor, will issue from the glass with a crackling noise, accompanied with sparks; this indicates the machine to be in good order, so that the electrician may proceed to perform his experiments. But if, when thecylinder is turned and the knuckle applied, no sparks be perceived, then the fault is most probably in the rubber. If so, it must be removed and held to a fire, so that its silk part may be dried. Then take a little tallow from a candle and just pass it over the leather of the cushion, after which spread upon it, a little amalgam, and force it as much as possible into the leather. Replace it, and let the cylinder be again wiped; the machine is fit for use.
4. Sometimes the electric matter will not be well collected, because the machine is not sufficiently supplied with it from the earth; which happens, when the table upon which the electrical machine is placed and to which the chain or wire of the rubber is connected, is very dry, and consequently a bad conductor. In this case, the best method is to connect the chain or wire of the rubber with some moist ground, or with the iron-work of a water-pump, if convenient. Thus the rubber will be supplied with as much of the electric fluid as is required.
5. When the cylinder is very hot (say above 110° of Fahrenheit’s thermometer,) it will not collect the electric fluid well.
6. When a sufficient quantity of amalgam has been accumulated upon the leather of the rubber, and the machine does not work well, then, instead of putting more upon it, a small quantity of that which is already on the leather must be taken off.
7. After the cylinder has been used for some time it will contract black streaks, which continually increase, and greatly obstruct its electric power.—These streaks must be taken off, and the glass frequently wiped to prevent their being again formed.
8. Coated jars, before they are used, ought to be made a little warm. If this be done, they will receive and retain the charge much better.
9. If one of the jars of a battery, as is sometimes the case, make a spontaneous discharge prematurely, it will of course discharge the whole battery; and in such case the faulty jar should be exchanged for one which is free from this defect.
10. In making the discharge of an electrical battery, or of a single jar, the electrician must be careful not to place the discharging-rod upon the thinnest part of the glass, as that may cause the bursting of the jar.
11. In large batteries, some of the jars frequently burst in the discharge. To remedy this inconvenience, Mr. Nairne says that the discharging-rod should never be made of a good conducting substance, except the circuit be at least five feet long. But here it may be remarked, that the length of the circuit weakens the force of the shock proportionably; the highest degree of which is in many instances required. When a coated phial is cracked, either by a spontaneous discharge or otherwise, the outside coating must be removed from the fractured part; then make it moderately hot by holding it near the fire; in this situation apply burning sealing-wax to the part, so as to cover the fracture completely, taking care that the thickness of the wax be rather more than the thickness of the glass; lastly, cover all the sealing-wax, and part of the glass beyond it, with a composition made of four parts of bee’s-wax, one of rosin, one of turpentine, and a little oil of olives: which composition must be spread upon a piece of oiled silk, and applied in the form of a plaister.In this manner jars which have been broken may be repaired effectually.
12. When a jar, and especially a battery, has been discharged, the wires ought not to be touched with the hand before the discharging-rod has been applied a second, and even a third time; as there generally remains a residuum of the charge, which is sometimes very powerful. This residuum is in a great measure occasioned by the electricity, which, when the jar is charging, spreads itself over the uncoated part of the glass, and which is not discharged at first, but gradually returns to the coating after the first discharge is made.
13. When an experiment is to be performed which requires only a small part of the apparatus, the remaining part should be removed from the table.—Candles should never be placed near the prime-conductor; for the effluvia of their flames carry off much of the electric matter.
14. One or two inches of the lower part of a Leyden phial should be coated with some thick paint, in order to prevent the amalgam, which is often scattered upon the table, from corroding the tin-foil, and thereby diminishing the charge.
15. When a prime-conductor is used, those sparks are strongest which are taken from the extremity farthest from the cylinder.
16. The longest sparks are drawn from any conductor along an electric substance. Thus, if the conductor be supported by pillars of glass or baked wood, the longest sparks may be taken close to the pillar. If the conductor be bent a little inward, so as to make the surface concave, a particularly large and undivided spark may be drawn from that place: but where thesurface is convex, the spark is more apt to be divided and weakened.
17. It sometimes happens that cylindric or globe machines do not work well, owing to the air within them being too much rarefied by the heat of the cement, when the caps are fixed on. To remedy this, a small hole may be bored through one of the caps, so as to admit air into the cylinder or globe.
18. If the electric by any means become scratched, the working of the machine will be greatly impeded, if not altogether prevented. This is accounted for upon the principle that smooth and rough glass electrify differently when excited by the same rubber, and the two different states destroy one another. This may be remedied by filling up the scratches with a little tallow.