The Press. — London, England, 1857-10-31 00:00:00

1066 battery. The crest of the pendulum lifts the one of these springs which it touches off the pillar for the time. When it lifts the right spring, it sends a current from the positive pole out through it and the wire, and back through the left spring to the negative pole or pillar. When it touches the left spring, it sends a current out through it and the wire the opposite way, and back through the right spring to the negative pole or pillar. The wire is coiled in different places round bars of soft iron. When the current passes through these coils, the bars become mag nets for the time, but the precise nature of thar magnetism depends on the direotion in which the currents run. • • • • • Having thus 1,146 miles of telegraphic cable under their hands and this delicate piece of scrutinising apparatus to work with in making investigations, the first fact to be determined by the experimenters was, could any avail able signal be transmitted through the 1,146 miles of con ductor. A seconds pendulum was first arranged to turn on the electrical current to the wire at each beat without attempting the reversal of the current. A trace appeared in a very short time under a style connected with the further end of the cable ; there could be no doubt of the ability of the electrical influence to make itself telegraphi cally manifest through that vast extent at least. There was, however, this curious anomaly in the result of the experiment. The pendulum made connection with the voltaic battery only for an instant at each beat ; but the printed trace on the paper was not interrupted. It was one long continuous line. The reason for this was, that the conducting wire did not discharge itself between beat and beat. The current moved so sluggishly and unwillingly in this protracted and indnction•encumbered channel, that one transmission was not able to clear itself oft, before the next was pressing upon its heels, and in confusion with it. Nut discouraged even by this result, the ex perimenters persevered, and their patience and ingenuity were rewarded by the discovery that, by sending rapid alternations of different kinds of electricity along the wire, seven, and even eight, currents readily recorded them selves distinctly in a second. So soon as this point was satisfactorily settled, the question arose, of what weight and size must be the Atlantic wire ? The reasons for adopting the particular size chosen for a conductor are not clearly stated. The results of two hundred experiments proved, we are told, that— Wire of increased capacity did not transmit electrical signals with greater facility and speed than the smaller one. With a length of 166 miles, the velocity of movement of the simple voltaic current came out •16 of a second for a single wire; •21 of a second for a double one ; and .28 for a treble one. With the same length, the velocity of the double induction current came out for the single wire, .08; with the double one, lig ; and with the treble one, .005 of a second. With a length of '250 miles, the velocity was for voltaic electricity, .29 and *406 of a second for a single and double wire respectively, and fur the double induction current, ' 145 and 'lB5 of a second. The fact thus actually is, that increasing the size of the conductor augments retardation in the trantimissicn of electricity through it. A treble-sized conductor gives nearly a doubled rate of retardation. Why not, then, use a much smaller conductor? That would have been the logical course to pursue, had the experimenters been convinced that the law here stated is correct. In the autumn of last year, so much had been settled that it only remained to actually record a signal through two thousand miles of circuit. Accordingly— On the night of the 9th of October, 1838, the conclave of experimenters met at the offices of the Magnetic Tele graph Company, in old Broad-street, Loudon, and the hours of ordinary repose were spent in carrying out the investigation which had been planned. The result was an unquestionable triumph. Ten gutta.percha covered insulated wires, each measuring more than 200 miles, were connected, so that one continuous circuit of above 2,000 miles was formed, the coils of fine wires introduced for experimental purposes at the joints of the wires further increasing the circuit virtually to the amount of 2,300 miles. The magneto-electric induction coils of Mr. Whitehouse were used to excite the wires, and the current was made to operate by means of receiving apparatus, upon one of l'rofessor Morse's ordinary recording instruments. Signals were distinctly and satisfactorily telegraphed through the two thousand miles of wire at the rate of 210, 241, and upon one occasion 21'0 per minute. No more emphatic expression of the importance of th-.. result of this experiment could perhaps be given, than the simple statement of the impression which was made upon the mind of the highly qualified and experienced American investigator, who was present as a witness. Shortly after the trial, Professor Morse wrote to the distinguished friend and advocate of Atlantic telegraphy, Mr. Cyrus Field, in tha following words :—" There can be no question but that, with a cable containing a single conducting wire of a a ze not exceeding that through which we worked, and with equal insulation, it would be easy to telegraph from Ireland to Newfoundland, at a speed of at least from eight to ten words per minute. Take it at ten words in the minute, and allowing ten words for name and address, we can safely calculate upon the transmission of a twenty words' message in three minutes. Twenty such messages in the hour ; four hundred and eighty in the twenty-four hours; or fourteen thousand four hundred words per day. Such are the capabilities of a single•wire cable, fairly and THE PRESS, OCTOBER 31,1857. moderately computed. It is, however, evident to me that by improvements in the arrangement of the signals them selves, aided by the adoption of a code or system constructed upon the principles of the best nautical code, as suggested by Mr. Whitehouse, we may at least double the speed in the transmission of our messages. In one word, the doubts are resolved; the difficulties are overcome; success is within our reach; and the great feat of the century must shortly be accomplished !" The magneto-electric induction coils here at tributed to Mr. Whitehouse are claimed by Mr. Thomas Allan, who in 1852 published, and we believe patented, this method of trans• mitted electricity. The weight of the cable which afterwards destroyed it is thus de scribed : The completed cable weighs from nineteen hundred weights to one ton per mile, and bears with impunity a direct strain of four tons being placed upon its strands. Some pieces have borne a direct strain of more than five tons without breaking. When, however, the cable is im mersed in sea water, its relative weight will, of course, be diminished. Its downward pressure in salt water will be a little under fourteen hundredweight per mile. The greatest depth over which the vessels will have to pass in depositing the cable in the Atlantic will be a little more than two miles; consequently it enough of the ropo were suffered to hang motionless from one of the vessels to reach the bottom in this depth, the strain needing to be borne by the rape would be under a ton and a half. During the process of paying out, however, the cable will be con stantly in motion, with only a sufficient restraining power upon it to control and regulate its egress from the ship, until this is by a rate slightly faster than the progress of the vessel. The strain will hence really be considerably less than a ton and a half for two miles. Here again another modifying influence also comes into play, to act still fur ther in the relief of the strain. The cable will not only be somewhat buoyed up, so to speak, by the water, it will also be buoyed up by the influence of friction. It will never descend, as it is payed out, in a vertical line, or reach the bottom in a course even approaching to a per pendicular direction. This will be because friction of the sides of the cable against the water will retard the sinking of the mass. The amount of this retardation, and the length which will consequently lie between the stern of the vessel and the bottom of the sea, will be determined by the rates at which the cable is payed out, and at which the paying-out vessel moves. In real fact, so far from there being any strain, consequent upon the weight of the cable, sufficient to injure its integrity, there will be only just pull enough to drag it gently out of the vessel over the revolving sheaves. The strain will be like the strain which is put on the filmy thread of the silkworm, as it is reeled rapidly off from the cocoon, and not like that which is put on a fixed rope, when a heavy weight is hung freely upon its lower end. The buoyancy and friction which will hinder the cable from dropping directly to the bottom of the sea, will sustain and uphold it as it falls. The specific gravity of the cable, and its flexibility, have been so planned that it will be laid down at the bottom of the ocean as gently as if it were passed through men's hands, or over pulleys all along its course in the yielding water. The frictional influence which will thus "lend a hand " to deposit the Telegraph Cable in the Atlantic, is identica with the cause of the regularly progressive diminution of the speed of the plummet's descent in deep-sea soundings, already alluded to in speaking of the method employed for elimi nating the horizontal pull of diversely moving currents, from the vertical drag of the plummet. There is, however, one important difference between the case of the cable and that of the sounding plummet. The plummet drags down a line which is lighter than the water, and which there fore has more buoyancy than friction attaching to its move ment. The cable is altogether heavierthan water, and has more friction than buoyancy. Friction will produce more retardation, comparatively, in the movement of the cable, than in that of the sounding plummet and line. It is easy now to see that this reasoning is fallacious ; but for mathematical proofs of this we must refer our readers to the scientific journals, or the proceedings of the British Association at Dahlia this year, where Cap tain Blakeley, 11. A., read a paper proving that a great and uninterrupted strain is necessary to prevent a great waste of cable, if the latter be heavy. Indeed, the projectors tell us (pp. 52 and 53) that they provided six hun dred miles of extra cable, although that be tween Varna and Balaklava was laid down during a storm with only three miles and three-quarters over the direct distance between the terminal stations. The reason is that the Black Sea cable was light, not covered with heavy iron wire to sustain its own weight during the process of submerging the cable only, after which we are told (p. 40) that " the " rust may cat up the irou external coat as " soon as it pleases." Mr. Bright, the engineer, confesses to re quiring 1,000 miles as a margin for next year. Are we to understand that a lighter, smaller, cheaper, and more easily conveyed cable would be curried away by currents into such curves as to require more than 1,000 miles of margin? Let the managers of the Atlantic Telegraph Company reconsider the question, and bear in mind that what they have already accom- plished gives them such a margin that the acknowledgment of an error will detract in nowise either from the admiration not only this but future generations must feel for the successful accomplishment—for successful it will be—of the most difficult and complicated piece of modern engineering, or from their gratitude for the beneficial results, obtained by such patient scientific research, backed by such patriotic enterprise. We say " patriotic enterprise," fur even in England 350,0001. aro not subscribed in a few days for an uncertain commercial speculation, without some other motive Were any proof of such philan• thropic motive of the shareholders wanting it has been furnished by their conduct since the failure of the first attempt., scarcely any having sold their shares. Not the least interesting portion of this little book is the description of the manufac ture of the cable, in which 332,500 miles of wire are used enough to engirdle the earth thirteen times. The central copper conductor itself is formed of seven wires twisted. This is next coated with three distinct layers of gutta percha, then with one of hemp and tar, and lastly with the fatal iron wire. For a description of the machi nery used we must refer our readers to the book itself, a perusal (we should perhaps say a study) of which will well reward the trouble. Victoria a•nd the Australian Gold Mines in 1857. By William Westgarth. London: Smith and Elder. BOOKS upon Australia on the average are uninterest ing. Whether it is that the writers are too preten tious, and disgust us with their Anglo-Saxon cant and their self•laudation, or whether they treat a dull subject in a heavy manner, we will not pretend to decide ; but of all the numerous books written these last few years upon Australia, with the exception of Colonel Mundy's " Our Antipodes "—and that was a little too llippaut—we have had scarcely one accurate, sensible, well-written book on the subject. Mr. Westgarth is perhaps the least pretentious and the most accurate of Australian writers. There is in his writing a strong fund of common sense and shrewd observation which is invaluable in a colonial writer, for we consult a colonial work more for accurate statement ar d sensible remark than for vivid descrip tion or brilliant antithesis. To be sure, if the two elements can be allied then we have nothing more to desire, but the first quality in a colonial writer is accuracy ; and so far we are bound to say that in whatever Mr. Westgarth treats of he may be relied upon. His only fault is a tendency to suppress rather than to exaggerate. He does not frankly tell us all the miseries that an immigrant must suffer in Victoria. With his extensive experience of the colony, he must be well aware that the hardships and inconveniences of life, and particularly of domes tic life, in Australia are very severe, for though indi vidually the ills of the country may appear trifling, yet in the aggregate they produce an amount of domestic misery that no one in this country accus tomed from childhood to the strictest personal cleanli ness could face without positive horror. Mr. Wust garth avoids all these points, and passes rapidly over the question of climate, which he admits is not healthy. We are glad to gather from his description of Australian politics that the land question is iu a fair way of being settled by compensation to the squatters. Au reate, his book, though wanting in careful detail, may be accepted as a very trustworthy volume upon the commerce and progress of Victoria in 1837. The Private Life of an Eastern King. By William Knighton. New Edition. London: Routledge. _ . . WE are glad to welcome our old friends again within the compass of Mr. Routledge's well known covers. The King and the barber, the five English gentlemen of his household, the grave Resident, and the laugh ing Nautch girl—man-eater, tiger, and ch..etah—all come before us again as interesting as ever, their charms enhanced by various respectable plates. The more we read these details the less we wonder at the pride proverbially attributed to the dynasty whose life they depict. Few of Mr. Routledge's cheap issues will be, we should think, more popular than this. Lives of Good Servants. By the Author of " Mary Powell." London : P.outledge. A VERY well conceived and useful little volume, adapted for presents to young servants, and con-