Part 6
We then find, page 576, the following statement: “Ingenious as Prof. Wheatstone’s, contrivances are, they would have been of no avail for telegraphic purposes, without the investigation which he was the first to make of the laws of electro magnets, when acted on through great lengths of wire. _Electro magnets of the greatest power, even when the most energetic batteries are employed, utterly cease to act when they are connected by considerable lengths of wire with the battery._”
If any thing were needed to show that Prof. Wheatstone was not the inventor of the _Electro Magnetic Telegraph_, it is this assertion (under the supervision of Prof. Wheatstone) made by Prof. Daniel. In 1843, Prof. Wheatstone had not made the discovery upon which Prof. Morse bases his invention, viz. that _Electro Magnets can be made to act, with an inconsiderable battery too, when the latter is connected with the former by considerable lengths of wire_: 80 miles may certainly be considered as of _considerable length_.
_Table constructed from the Curve._
Battery alone 5.20 inches. 1 mile 3.85 “ 2 “ 2.62 “ 3 “ 1.84 “ 4 “ 1.20 “ 5 “ 1.05 “ 6 “ .92 “ 7 “ .80 “ 8 “ .71 “ 9 “ .64 “ 10 “ .57 “ 20 “ .30 “ 30 “ .20 “ 40 “ .14 “ 50 “ .094 “
During the previous summer, I made the following experiments, upon a line of 33 miles, of number 17 copper wire, with a battery of 50 pairs. In this case, I used a small steelyard, with weights, with which I was enabled to weigh, with a good degree of accuracy, the greater magnetic forces, but not the lesser, yet sufficiently approximating the recent results to confirm the law in question.
_Table of Results._
50 pairs through 2 miles attracted and raised 9 ozs. “ 4 “ “ “ 4 “ “ 6 “ “ “ 3 “ “ 8 “ “ “ 2½ “ “ 10 “ “ “ 2¼ “ “ 12 “ “ “ ⅛ “ “ 14 “ “ “ ⅛ “
and each successive addition of two miles, up to 33, still gave an attractive and lifting power of one-eighth of an ounce.
_Curve from these Results._
It has been objected, that if the conducting power of wires, for electricity was inversely as their length, and directly as their section, the transmission of telegraphic signals, through long wires, could not be carried into effect, and even the galvanic multiplier, which consists, essentially, of a wire making several convolutions round a needle, could have no existence. This last objection was first brought forward by Prof. Ritchie, of the University of London, as an absolute proof, that the law referred to is incorrect. There is, however, an exceedingly simple method of proving that signals may be despatched through very long wires, and that the galvanic multiplier, so far from controverting the law in question, depends for its very existence upon it.
Assuming the truth of the law of Lenz, the _quantities_ of electricity which can be urged by a constant electromotoric source through a series of wires, the lengths of which constitute an arithmetical ratio, will always be in a geometrical ratio. Now the curve whose ordinates and abscissas bear this relation to each other, is the logarithmic curve whose equation is _aʸ_ = _x_.
1st. If we suppose the base of the system, which the curve under discussion represents, be greater than unity, the values of _y_ taken between _x = 0_, and _x = 1_, must be all negative.
2d. By taking _y = 0_, we find that the curve will intersect the axis of the _x_’s, at a distance from the origin, equal to unity.
3d. By making _x = 0_, we find _y_ to be infinite and negative. Now, these are the properties of the logarithmic curve, which furnish an explanation of the case in hand. Assuming that the _x_’s represent the quantities of electricity, and the _y_’s the lengths of the wires, we perceive at once, that those parts of the curve which we have to consider, lie wholly in the fourth quadrant, where the abscissas are positive and the ordinates negative. When, therefore, the battery current passes without the intervention of any obstructing wire, its value is equal to unity. But, as successive lengths of wire are continually added, the quantities of electricity passing, undergo a diminution, at first rapid, and then more and more slow. And it is not until the wire becomes infinitely long that it ceases to conduct at all; for the ordinate _y_, when _x = 0_, is an asymptote to the curve. In point of practice, therefore, when a certain limit is reached, the diminution of the intensity of the forces becomes _very small_, whilst the increase in the lengths of the wire is vastly great. It is, therefore, possible to conceive a wire to be a million times as long as another, and yet, the two shall transmit quantities of electricity not perceptibly different, when measured by a delicate galvanometer. But, under these circumstances, if the long wire be coiled, so as to act as a multiplier, its influence on the needle will be inexpressibly greater than the one so much shorter than it. Further, from this we gather that for telegraphic despatches, with a battery of given electromotoric power, when a certain distance is reached, the diminution of effect for an increased distance becomes inappreciable.
THE GALVANOMETER OR GALVANOSCOPE.
This useful instrument, the invention of which is based upon Oersted’s discovery of the deflection of the magnetic needle, by the action of conducting wires conveying galvanic currents, seems to have furnished to most of the inventors of telegraphs, the main spring of communication. It was a very natural suggestion, as being the most convenient and ready mode of obtaining the required motion, by making and breaking the galvanic circuit. Thus Steinheil, Wheatstone and Bain have availed themselves of this _one idea_ to effect that part of the telegraphic operation which may be called the _galvanic_, in contradistinction to the _mechanical_ parts, which last have varied considerably with different operators. The construction and operation of the galvanometer may be understood by reference to the figures 27, 28, 29. A A, fig. 28, are two long coils of covered copper wire, a side view of which is shown in fig. 27. These coils are connected with the binding screws, L L, attached to the frame, or box, holding the coils. Two coils are used for the convenience of allowing the pivot sustaining the magnetic needle to pass between them; one coil might be used, by leaving room enough between the wires for a socket for the pivot, but the arrangement, represented, is the most readily constructed. A side view of the instrument, figure 27, shows the arrangement of the needles, two of them being generally used to increase the operation of deflection, and to neutralize the influence of the earth’s magnetism. The pair of needles is usually denominated, an _astatic_ needle, or a needle without directive power; as the current traversing a conducting wire gives different directions to needles placed above and below the wire, the action upon the two needles thus placed is combined, by arranging their poles in opposite directions. When the current is in the direction indicated by the arrows in figure 27, the north pole of the needle, within the coil, is carried in a direction from you, as you face the drawing, and the north pole, without the coil, in a contrary direction. The operation upon the south pole is the reverse. Changing the direction of the galvanic current, reverses the motions. It is usual to apply the force of torsion, or of a _hair_ spring, or of the superior weight of one extremity of the needle, to act against the deflective force of the current, and to attach a graduated scale to the instrument, fixing it between the uppermost needle and the coils as in figure 29. Instead of deflecting the needle, the coils themselves may be deflected, as in the galvanoscope of Prof. Page, invented in January, 1837, and described by him in the 33d vol. of Silliman’s Journal, page 376. The object of this contrivance was to enable him to use powerful magnets and lighter coils. This modification of the galvanoscope, Mr. Bain has preferred as the means of operating his telegraph.
_An Interesting Experiment of Supporting a Large Bar of Iron within the Helix. Discovered by Mr. Vail, January, 1844._
It has been shown, many years since, that a magnetic needle would be drawn into and suspended within a helix, conveying a galvanic current, and that in the case of using large bar magnets, the coils or helices might be made to move over them, as in De La Rives’s rings; but in no instance, I believe, has it been recorded, or observed, that a bar of iron weighing a pound or more, could be drawn up into the helix and there sustained in the air, as it were, without support. If the helix, as shown in figure 30, be connected with from 6 to 12 pairs of Grove’s battery, the bar may be drawn up into its centre and there sustained in a vertical position by the action of the helix, forming an exceedingly interesting and paradoxical experiment.
[From the National Intelligencer.]
APPLICATION OF THE ELECTRO MAGNETIC TELEGRAPH TO THE DETERMINATION OF LONGITUDE.
Among the wonderful developements of the new telegraph, one has just came to light which will be regarded in the world of science as deeply interesting. Prof. Morse suggested to the distinguished Arago, in 1839, that the electro magnetic telegraph would be the means of determining the difference of longitude between places with an accuracy hitherto unattainable. By the following letter from Capt. Charles Wilkes to Prof. Morse, it will be believed that the first experiment of the kind of which we have any knowledge, has resulted in the fulfilment of the Professor’s prediction.
WASHINGTON, _June 13, 1844_. MY DEAR SIR—The interesting experiments for obtaining the difference of longitude through your magnetic telegraph were finished yesterday and have proved very satisfactory. They resulted in placing the Battle Monument square, Baltimore, 1 _m_, .34 sec. .868 east, of the capitol. The time of the two places was carefully obtained by transit observations. The comparisons were made through chronometers and without any difficulty. They were had in three days, and their accuracy proved in the intervals marked and recorded at both places. I have adopted the results of the last day’s observations and comparisons, from the elapsed time having been less.
The difference of the former results, found in the American Almanac, is .732 of a second. After these experiments, I am well satisfied that your telegraph offers the means for determining meridian distances more accurately than was before within the power of instruments and observers.
Accept my thanks, and those of Lieutenant Eld, for yourself and Mr. Vail, for your kindness and attention in affording us the facilities to obtain these results. With great respect and esteem, your friend, CHARLES WILKES. Professor S. F. B. MORSE, _Capitol, Washington_.
MODE OF CROSSING BROAD RIVERS, OR OTHER BODIES OF WATER, WITHOUT WIRES.
The following extract from Professor Morse’s letter to the Secretary of the Treasury, and by him submitted to the House of Representatives, Dec. 23, 1844, in relation to this interesting subject, will sufficiently illustrate it:
“In the autumn of 1842, at the request of the American Institute, I undertook to give to the public in New York a demonstration of the practicability of my telegraph, by connecting Governor’s Island with Castle Garden, a distance of a mile; and for this purpose I laid my wires properly insulated beneath the water. I had scarcely begun to operate, and had received but two or three characters, when my intentions were frustrated by the accidental destruction of a part of my conductors by a vessel, which drew them up on her anchor, and cut them off. In the moments of mortification, I immediately devised, a plan for avoiding such an accident in future, by so arranging my wires along the banks of the river as to cause the water itself to conduct the electricity across. The experiment, however, was deferred till I arrived in Washington; and on December 16, 1842, I tested my arrangement across the canal, and with success. The simple fact was then ascertained, that electricity could be made to cross a river without other conductors than the water itself; but it was not until the last autumn that I had the leisure to make a series of experiments to ascertain the law of its passage. The following diagram will serve to explain the experiment.
A, B, C, D, are the banks of the river; N, P, are the battery; E is the electro magnet; _w w_, are the wires along the banks, connecting with copper plates, _f_, _g_, _h_, _i_, which are placed in the water. When this arrangement is complete, the electricity, generated by the battery, passes from the positive pole, P, to the plate _h_, across the river through the water to plate _i_, and thence around the coil of the magnet, E, to plate _f_, across the river again to plate _g_, and thence to the other pole of the battery, N. The numbers 1, 2, 3, 4, indicate the distance along the bank measured by the number of times of the distance across the river.
The distance across the canal is 80 feet; on August 24th, the following were the results of the experiment.
+-------+--------+------+-------+-------+-------- No. of the | 1st. | 2d. | 3d. | 4th. | 5th. | 6th. experiment, | | | | | | ---------------------+-------+--------+------+-------+-------+-------- No. of cups in | | | | | | battery, | 14 | 14 | 14 | 7 | 7 | 7 Length of conductors,| | | | | | _w_, _w_, | 400 | 400 | 400 | 400 | 300 | 200 Degrees of motion of | | | | | | galvanometer, |32 & 24|13½ & 4½| 1 & 1|24 & 13|29 & 21|21½ & 15 Size of the copper | | | | | | plates | | | | | | _f_, _g_, _h_, _i_, |5 by 2½|16 by 18|6 by 5|5 by 2½|5 by 2½| 5 by 2½ | ft.| in.| in.| ft.| ft.| ft. ---------------------+-------+--------+------+-------+-------+--------
Showing that electricity crosses the river, and _in quantity in proportion to the size of the plates in the water._ The _distance of the plates on the same side_ of the river _from each other_ also affects the result. Having ascertained the general fact, I was desirous of discovering the best practical distance at which to place my copper plates, and not having the leisure myself, I requested my friend Professor Gale to make the experiments for me. I subjoin his letter and the results.
NEW YORK, _November_ 5th, 1844. MY DEAR SIR—I send you, herewith, a copy of a series of results, obtained with four different sized plates, as conductors to be used in crossing rivers. The batteries used were six cups of your smallest size, and one liquid used for the same throughout. I made several other series of experiments, but these I most rely on for uniformity and accuracy. You will see, from inspecting the table, that the distance along the shores should be _three times greater_ than that from shore to shore across the stream; at least, that four times the distance does not give any increase of power. I intend to repeat all these experiments under more favorable circumstances, and will communicate to you the results. Very respectfully, L. D. GALE.
Professor S. F. B. MORSE, _Superintendent of Telegraphs_.
Series of Experiments on four different sizes of plates, to wit: 1st, 56 square inches; 2d, 28 square inches; 3d, 14 square inches; and 4th, 7 square inches.
_Experiment 1st.—Surface of one face of the copper plate, 56 square inches; battery, Morse’s smallest, 6 cups._
NOTE.—In all the experiments, _f_ and _g_ are stationary. --------+--------+---------+---------+------+------+------+------ Distance| | | | | | | from |Distance| | | | | | bank | along | 1st | 2d | 3d | 4th | 5th | 6th to bank.| shore | Trial. | Trial. |Trial.|Trial.|Trial.|Trial. --------+--------+---------+---------+------+------+------+------ 1 | 1 | 22° | 23° | 23° | 22° | 22° | 22° --------+--------+---------+---------+------+------+------+------- 1 | 2 | 31 | 32 | 31½ | 31 | 31 | 31 --------+--------+---------+---------+------+------+------+------- 1 | 3 | 36 | 36 | 35½ | 35 | 35 | 35 --------+--------+---------+---------+------+------+------+------- 1 | 4 | 36 scant| 36 scant| 34½ | 34 | 34 | 34 --------+--------+---------+---------+------+------+------+-------
_Experiment 2d.--Plates 28 square inches, conducted as above._ --------+--------+-------+-------+-------+-------+----------+------- Distance| | | | | | | from |Distance| | | | | | bank | along | 1st | 2d | 3d | 4th | 5th | 6th to bank.| shore | Trial.| Trial.| Trial.| Trial.| Trial. | Trial. --------+--------+-------+-------+-------+-------+----------+------- 1 | 1 | 18° | 17° | 17° | 17° | 17° | 17° --------+--------+-------+-------+-------+-------+----------+------- 1 | 2 | 27 | 26 | 27½ | 27½ | 27½ | 27 --------+--------+-------+-------+-------+-------+----------+------- 1 | 3 | 31 | 31 | 31 | 31 | 31 | 31 --------+--------+-------+-------+-------+-------+----------+------- 1 | 4 | 31 | 31 | 31 | 31 | 31 scant.| 31 --------+--------+-------+-------+-------+-------+----------+-------
_Experiment 3d.--Plates 14 square inches, conducted as No. 1._ -------------+-----------+------+------+------+------+------+------ Distance from| Distance | 1st | 2d | 3d | 4th | 5th | 6th bank to bank.|along shore|Trial.|Trial.|Trial.|Trial.|Trial.|Trial. -------------+-----------+------+------+------+------+------+------ 1 | 1 | 8° | 8½° | 8½ | 8° | 8° | 8° 1 | 2 | 19½ | 20 | 19½ | 19 | 19 | 19 1 | 3 | 23½ | 23½ | 23½ | 23½ | 23½ | 23½ 1 | 4 | 24½ | 24½ | 23½ | 23½ | 23½ | 23½ -------------+-----------+------+------+------+------+------+------
_Experiment 4th.--Plates 7 square inches, conducted as No. 1._ -------------+-----------+------+------+------+------+------+------ Distance from| Distance | 1st | 2d | 3d | 4th | 5th | 6th bank to bank.|along shore|Trial.|Trial.|Trial.|Trial.|Trial.|Trial. -------------+-----------+------+------+------+------+------+------ 1 | 1 | 5° | 5° | 5° | 5° | 3° | 3° 1 | 2 | 15 | 14½ | 14 | 15 | 15 | 12 1 | 3 | 17½ | 18 | 17½ | 17½ | 18 | 17 1 | 4 | 18 | 18 | 18 | 17½ | 17½ | 17 -------------+-----------+------+------+------+------+------+------
The distance from bank to bank, 30 inches. Depth of water, 12 inches. In experiment 4, the liquor of the batteries was very weak, exhausted towards the last; and in trials 5 and 6, the irregularities are to be attributed in part to the weak liquor, and in part to the twilight hour at which the experiments were made.
As the result of these experiments, it would seem that there may be situations in which the arrangements I have made for passing electricity across the rivers may be useful, although experience alone can determine whether lofty spars, on which the wires may be suspended, erected in the rivers, may not be deemed the most practical. The experiments made were but for a short distance; in which, however, the principle was fully proved to be correct. It has been applied under the direction of my able assistants, Messrs. Vail and Rogers, across the Susquehanna river, at Havre-de-Grace, with complete success; a distance of nearly a mile.
TELEGRAPHIC CHESS PLAYING
In order to give some idea of the accuracy with which the telegraph transmits intelligence, we here give two games of chess, as played by distinguished gentlemen in Baltimore and in Washington. The two games are selected from the seven played. The number of moves made in playing the seven games, were 686, and were transmitted without a single mistake or interruption. The Baltimoreans played with the white pieces, placed on numbers 57, 58, 59, 60, 61, 62, 63, and 64, figure 32. They were commenced November 16th, 1844. B, Baltimore; W, Washington.
_First Game of Chess._
W 12 to 28 B 53 “ 37 W 6 “ 30 B 51 “ 46 W 7 “ 22 B 52 “ 36 W 28 “ 36 B 46 “ 36 W 30 “ 18 B 63 “ 46 W 13 “ 20 B 56 “ 41 W 9 “ 24 B 58 “ 43 W castles B 59 to 45 W 14 “ 19 B 45 “ 51 W 3 “ 21 B 61 “ 45 W 22 “ 5 B 55 “ 39 W 2 “ 17 B 49 “ 48 W 19 “ 30 B 36 “ 29 W 21 “ 13 B 39 “ 26 W 11 to 29 B 26 “ 24 W 10 “ 23 B 62 “ 26 W 4 “ 3 B 43 “ 40 W 30 “ 35 B 45 “ 42 W 7 “ 9 B 40 “ 23 W 5 “ 14 B 23 “ 6 W 3 “ 6 B castles 60 to 62 & 64 “ 61 W 17 to 30 B 26 “ 38 W 14 “ 5 B 57 “ 58 W 30 “ 45c B 51 “ 45 W 35 “ 45 B 42 “ 23c W 9 “ 8 B 61 “ 52 W 27 “ 37 B 24 “ 9 B 18 “ 36 B 23 “ 7 W gives up.
_Second Game._