PROGRESS OF SCIENCE, &c. ELECTRIC FORCE OF THE GYMNOTUS. NOTICE of the Electric Force of the Gymnotus, or Electric Eel, now in the Adelaide Gallery. From Faraday's Experimental Researches in Electricity. "I first experimented with it on the 3rd of September, when it was apparrently languid, but gave strong shocks when the hands were favourably disposed on the body. The experiments were made on four different days, allowing periods of rest from a month to a week between each. His health seemed to improve continually, and it was during this period, between the third and fourth days of experiment, that he began to eat. "Beside the hands two kinds of collectors were used. The one sort consisted each of a copper rod fifteen inches long, having a copper disc one inch and a half in diameter brazed to one extremity, and a copper cylinder to serve as a handle, with large contact to the hand fixed to the other, the rod from the disc upwards being well covered with a thick caoutchouc tube to insulate that part from the water. By these the states of particular parts of the fish whilst in the water could be ascertained. "The other kind of collectors were intended to meet the difficulty presented by the complete immersion of the fish in water; for even when obtaining the spark itself I did not think myself justified in asking for the removal of the animal into air. A plate of copper eight inches long by two inches and a half wide, was bent into a saddle shape, that it might pass over the fish, and inclose a certain extent of the back and sides, and a thick copper wire was brazed to it, to convey the electric force to the experimental apparatus; a jacket of sheet caoutchouc was put over the saddle, the edge projecting at the bottom and the ends; the ends were made to converge so as to fit in some degree the body of the fish, and the bottom edges were made to spring against any horizontal surface on which the saddles were placed. The part of the wire liable to be in the water was covered with caoutchouc. "These conductors being put over the fish, collected power sufficient to produce many electric effects; but when, as in obtaining the spark, every pos sible advantage was needful, then glass plates were placed at the bottom of the water, and the fish being over them, the conductors were put over it until the lower caoutchouc edges rested on the glass, so that the part of the animal within the caoutchouc was thus almost as well insulated as if the Gymnotus had been in the air. "Shock. The shock of this animal was very powerful when the hands were placed in a favourable position, i.c. one on the body near the head, and the other near the tail; the nearer the hands were together within certain limits the less powerful was the shock. The disc conductors conveyed the shock very well when the hands were wetted and applied in close contact with the cylindri cal handles; but scarcely at all if the handles were held in the dry hands in an ordinary way. "Galvanometer. Using the saddle conductors applied to the anterior and posterior parts of the Gymnotus, a galvanometer was readily affected. It was not particularly delicate; for zinc and platina plates on the upper and lower surface of the tongue did not cause a permanent deflection of more than 25o; yet when the fish gave a powerful discharge the deflection was as much as 30o, and in one case even 40°. The deflection was constantly in a given direction, the electric current being always from the anterior parts of the animal through the galvanometer wire to the posterior parts. The former were therefore for the time externally positive, and the latter negative. "Making a magnet. When a little helix containing twenty-two feet of silked wire wound on a quill was put into the circuit, an annealed steel needle placed in the helix, the needle became a magnet, and the direction of its polarity in every case indicated a current from the anterior to the posterior parts of the Gymnotus through the conductors used. "Chemical decomposition. Polar decomposition of a solution of iodide of potassium was easily obtained. Three or four folds of paper moistened in the solution were placed between a platina plate and the end of a wire also of platina, these being respectively connected with the two saddle conductors. Whenever the wire was in conjunction with the conductor at the fore part of the Gymnotus, iodine appeared at its extremity; but when connected with the other conductor none was evolved at the place on the paper where it before appeared. So that here again the direction of the current proved to be the same as that given by the former tests, "By this test I compared the middle part of the fish with other portions before and behind it, and found that the conductor A, which being applied to the middle was negative to the conductor B applied to the anterior parts, was, on the contrary, positive to it when B was applied to places near the tail. So that within certain limits the condition of the fish externally at the time of the shock appears to be such, that any given part is negative to other parts anterior to it, and positive to such as are behind it. "Evolution of heat. Using a Harris's thermo-electrometer belonging to Mr. Gassiot, we thought we were able in one case, namely, that when the deflection of the galvanometer was 40°, to observe a feeble elevation of temperature. I was not observing the instrument myself, and one of those who at first believed they saw the effect now doubts the result. 66 Spark. The electric spark was obtained thus. A good magneto-electric coil, with a core of soft iron wire, had one extremity made fast to the end of one of the saddle collectors, and the other fixed to a new steel file; another file was made fast to the end of the other collector. One person then rubbed the point of one of these files over the face of the other, whilst another person put the collectors over the fish, and endeavoured to excite it to action. By the friction of the files contact was made and broken very frequently; and the object was to catch the moment of the current through the wire and helix, and by breaking the contact during the current to make the electricity sensible as a spark. "The spark was obtained four times, and nearly all who were present saw it. That it was not due to the mere attrition of the two piles was shown by its not occurring when the files were rubbed together, independently of the animal. Since then I have substituted for the lower file a revolving steel plate, cut file fashion on its face, and for the upper file wires of iron, copper and silver, with all of which the spark was obtained.+ "Such were the general electric phænomena obtained from this Gymnotus whilst living and active in its native element. On several occasions many of them were obtained together; thus a magnet was made, the galvanometer deflection, and perhaps a wire heated, by one single discharge of the electric force of the animal. "I think a few further but brief details of experiments relating to the quantity and disposition of the electricity in and about this wonderful animal will not be out of place in this short account of its powers. "When the shock is strong, it is like that of a large Leyden battery charged to a low degree, or that of a good voltaic battery of perhaps one hundred or more pairs of plates, of which the circuit is completed for a moment only. 1 endeavoured to form some idea of the quantity of electricity by connecting a large Leyden battery with two brass balls, above three inches in diameter, placed seven inches apart in a tub of water, so that they might represent the parts of the Gymnotus to which the collectors had been applied; but to lower the intensity of the discharge, eight inches in length of six-fold thick wetted string were interposed elsewhere in the circuit, this being found necessary to prevent the easy occurrence of the spark at the ends of the collectors, when they are applied in water near to the balls, as they had been before to the fish. Being thus arranged, when the battery was strongly charged and discharged, and the * In more recent experiments of the same kind we could not obtain the effect. + At a later meeting, at which attempts were made to cause the attraction of gold leaves, the spark was obtained directly between fixed surfaces, the inductive coil being removed, and only short wires (by comparison) employed. hands put into the water near the balls, a shock was felt, much resembling that from the fish; and though the experiments have no pretension to accuracy, yet as the tension could be in some degree imitated by reference to the more or less ready production of a spark, and after that the shock be used to indicate whether the quantity was about the same, I think we may conclude that a single medium discharge of the fish is at least equal to the electricity of a Leyden battery of fifteen jars, containing 3500 square inches of glass coated on both sides, charged to its highest degree. This conclusion respecting the great quantity of electricity in a single Gymnotus shock, is in perfect accordance with the degree of deflection which it can produce in a galvanometer needle, and also with the amount of chemical decomposition produced in the electrolyzing experiments. "Great as is the force in a single discharge, the Gymnotus, as Humboldt describes, and as I have frequentfy experienced, gives a double and even triple shock; and this capability of immediately repeating the effect with scarcely a sensible interval of time, is very important in the considerations which must arise hereafter respecting the origin and excitement of the power in the animal. Walsh, Humboldt, Gay-Lussac, and Montucci have remarked the same thing of the Torpedo, but in a far more striking degree.” ON THE APPLICATION OF ELECTRO-MAGNETISM AS A MOTIVE POWER; In a Letter from Prof. P. Forbes, of Aberdeen, to Michael Faraday, D.C.L., &c. &c. "King's College, Aberdeen, Oct. 7, 1839. "MY DEAR SIR, "HAVING seen a notice from Mr. Jacobi sent by you to the London and Edinburgh Philosophical Magazine, regarding the success of his experiments on the production of a moving power by electro-magnetism, I am sure it will give you pleasure to know that a countryman of our own, Mr. Robert Davidson, of this place, has been eminently successful in his labours in the same field of discovery. For in the first place, he has an arrangement by which with only two electro magnets and less than one square foot of zinc surface (the negative metal being copper) a lathe is driven with such velocity as to be capable of turning small articles. Secondly, he has another arrangement, by which, with the same small extent of galvanic power, a small carrage is driven on which two persons were carried along a very coarse wooden floor of a room. And he has a third arrangement, not yet completed, by wbich, from the imperfect experiments he has made, he expects to gain very considerably more force from the same extent of galvanic power than from either of the other two. "The first two of these arrangements were seen in operation by Dr. Fleming, Professor of Natural Philosophy in this University, and myself, some days ago; and there remains no doubt on our minds that Mr. Davidson's arrangements will, when finished, be found available as a highly useful, efficient, and exceedingly simple moving power. He has been busily employed for the last two years in his attempts to perfect his machines, during all which time I have been acquainted with his progress, and can bear testimony to the great ingenuity he has shown in overcoming the numberless difficulties he has had to encounter. So far as I know, he was the first who employed the electromagnetic power in producing motion by simply suspending the magnetismn without a change of poles. This he accomplished about two years ago. About the same time he also constructed galvanic batteries on Professor Daniell's plan, by substituting a particular sort of canvas instead of gut, which substitution answers perfectly, is very durable, and can be made of any form or size. And, lastly, he has ascertained the kind of iron, and the mode of working it into the best state for producing the strongest magnets with certainty. The first two machines, seen in operation by Dr. Fleming and myself, are exceedingly simple, without indeed the least complexity, and therefore easily manageable, and not liable to derangement. They also take up very little room. As yet the extent of power of which they are capable has not been at : all ascertained, as the size of battery employed is so trifling and the magnets so few but from what can be judged by what is already done, it seems to be probable that a very great power, in no degree even inferior to that of steam, but much more manageable, much less expensive, and occupying greatly less space, if the coals be taken into account, may be obtained. "In short, the inventions of Mr. Davidson seem to be so interesting, to railroad proprietors in particular, that it would be much for their interests to take up the subject, and be at the expense of making the experiments necessary to bring this power into operation on the great scale, which indeed would be very trifling to a company, while it is very serious for an individual by no means rich, and who has already expended so much of his time and money from the mere desire of perfecting machines which he expected would be so beneficial to his country and to mankind. For it deserves to be mentioned that he has made no secret of his operations, but has shown and explained all that he has done to every one who wished it. His motives have been quite disinterested, and I shall deem it a reproach to our country and countrymen if he is allowed to languish in obscurity, and not have an opportunity afforded him of perfecting his inventions and bringing them into operation, when they promise to be productive of such incalculable advantages. "Michael Faraday, D.C.L., &c. &c." "I am, my dear Sir, yours, &c, "PAT. FORBES." PAPER-CUTTING MACHINE. Ar Loch paper mill, near Linlithgow, an improved cutting machine has been at work these four months past, constructed and fitted up by the enterprising genius of Mr. John Brown, engineer, Anderson, Glasgow. It is of a very simple construction, and will certainly be a great benefit to paper manufacturers in cutting sheets of a size to the greatest nicety, without broke; pot paper 240 sheets per minute, or 360 reams per twelve hours; other sizes in proportion. It has been examined by several gentlemen in the paper trade, and considered a superior invention. METEOROLOGICAL REPORT, FROM OCT. 21ST TO Nov. 21st, 1839. We have had another month of heavy and long continued rain, but it has been of a character quite different from autumnal and winterly rains in general. It is usual at this season of the year, for the rain to begin from the South and to continue longer or shorter, till it is chased away by a strong wind from the West During the last month, however, nearly all the rain has come from the Eastward, and there has been no tempestuous tendency whatever, The first fall of rain commenced on the 23d, of October and lasted as usual about twenty-four hours. The wind then settled in the north-east and remained there till the 4th. of November. October 27 and 28, driving showers of hail and rain. 29th, and three following days, it blew very strong. November 3, heavy rain at night, which lasted till noon the next day, when the wind shifted to the south-west. Nov 7, rain again at night from the east, which was in part repeated on the next day. Nov. 9, rain from the old quarter, which began at night and lasted till midnight of the 10th, with little interruption, and at times being heavy. The 11th was a fine day, the 12th. and 13th foggy, and on the 14th. rain for some hours from the south-east. On the 16th, the wind got quite away from the east, and the 20th was a very fine day, with a westerly wind pointing to the north. At night the sky was beautifully clear, and by seven o'clock, the frost had whitened the ground, but the wind again dropped into the everlasting south-east, and soon after midnight, the rain descended, almost in torrents. Overcast, small rain, damp day, fog morning and evening. 24 29-72 30.00 50 49 49 50 47 SE. 2 ESE. 3 SE. 2 .332 48 51 48 51 42 NE. 2 NE. 3 NE. 2 326 26 30.02 45 50 46 52 42 N. 2 N. 3 N. 3 ⚫011 Small rain all day, fog at night. Overcast, little sun at 2 P.M. afterwards rain. Sun, cloudless till 11 A.M. little rain at 3 P.M. evening fine. Sun and light clouds, night clear. Overcast, a little very small rain P.M. Overcast, very damp, showers. Overcast, drizzling rain, dull uncomfortable day. Heavy rain till 12 A.M. cloudy, damp and foggy P.M. Overcast, a few breaks in the S.E. Overcast, small rain at times 332 S. 3 SE. SW. 3 S. 2 SSW. 2 SE. 2 8. SW. 3 SSW. 2 221222 .006 Overcast, small rain A.M. rain at 6 P.M. *085 Overcast, rain at 54 P.M. fog at night. 215 Overcast, rain from 104 A.M. wet day. .862 Sun, many clouds, fine day but rather misty. Thick fog all day, small rain at 5 P.M. ⚫015 Overcast, foggy, small rain at times ⚫012 Overcast, rain, uncomfortable day Sw. 2 SW. 2 SSW. 3 S. 3 Overcast, small rain, very damp day. Overcast till noon, sun, many clouds till 2, clear at 6 P.M. R. N. HARRIS. W. Dearden, Printer, Nottingham. |