fused through lines, if thought best, avoiding the necessity of keeping up immense batteries at terminal stations. Eighthly-It also enables the operator, in a short time, to vary at pleasure the quantity of battery-force he may desire to use, since larger or smaller plates can be used, or the same plates can be immersed more or less in the solution. We now come to consider its value as regards intensity, in comparison with Grove's. And here we must ask, What is a Grove's battery in use upon telegraph lines? It certainly is not the battery as first put up with fresh nitric acid, for, to keep up that strength, you must put in entirely new acid every twelve hours; and in practice, this is only supplied once in two weeks. A battery that has been used three days is considered, by most experts, of average power. The degrees below exhibit the power of the new battery after four days' use, and are degrees of the dynameter dial:— A comparison of these figures with those representing the power of Grove's, establishes the remarkable fact that the new battery increases faster in intensity as the series progresses than Grove's; and hence the power of the two batteries in ascending series approximates. But while the new battery requires a much greater number of cups to accomplish a given intensity than the nitric acid arrangement, this intensity, no matter how great, can be obtained to any extent, and much more rapidly, as the series extends; and once obtained, it becomes a fixed fact. A series of one hundred and twenty-five cups had not lost one-twentieth of its power in four days; and the extent of the series has not the slightest tendency to produce cross-fire, one hundred and twenty-five cups in one series being as quiet as five cups. Whereas, the number of cups in a series of Grove's effects cross-fire in a geometrical ratio, as we have before seen. As practical test of the battery, it has worked from New-York to Boston twenty-three days, under my supervision, supplying the current night and day during that time. Two hours' time has been spent in taking care of it since first setting it up; and about three ounces of zinc have been used. It has also worked from New-York to Philadelphia, without taking down for two months, only demanding a trifling attention once a week. It is also working the extended circuit from New-York to Buffalo with perfect success. Its practical working has confirmed the theory, and realized the most sanguine expectations of its in ventor. Art. VIII.-RAILROAD BRIDGE AND SWITCH TELEGRAPH. WE give below some extracts from the "Journals of the Franklin Institute of the State of Pennsylvania," relative to a telegraph system invented by Mr. William C. McRea, of Philadelphia, for railroad purposes. We understand that the inventor is one of the practical and well-informed telegraphers, and is worthy of the most liberal consideration of gentlemen engaged in that science and art. While we entertain the expectation of early witnessing the application of the art of telegraphing to the purposes of railroads, we cannot well understand how the measure can be consummated at the small expense we have frequently seen estimated. With proper care, and perfectly insulating the conductors, the telegraph can be made to subserve the most commanding wants of the railroad enterprise, by preserving life, economy, and regularity of running. We shall be pleased to hear of the experiments in railroad telegraphs, and hope Mr. McRea will favor us with all the particulars. EDITOR. HALL OF THE FRANKLIN INSTITUTE, The Committee on Science and the Arts, constituted by the Franklin Institute of the State of Pennsylvania, for the promotion of the Mechanic Arts, to whom was referred for examination a Railroad Drawbridge and Switch Safety Telegraph, invented by Mr. Wm. C. McRea, of Philadelphia, Pennsylvania, REPORT: That in this contrivance, an electric current is arranged so as to be closed when the drawbridge is in proper position, and to be broken when this is not the case. The wire terminates in a rail carefully isolated from the rest of the track, and at such a distance from the bridge as to allow ample room for stopping the train of cars between them. The next rail to the one spoken of is also isolated from the track, and connected with one of the ground plates of the circuit. On the locomotive is placed an electric magnet of the ordinary construction, whose keeper controls the works of an alarm, so that the bell, stopped while 3 VOL. I.-NO. V. * the keeper is not attracted by the magnet, is released, and allowed to ring the moment that this attraction takes place. The wire of the coil terminates in metallic connection with the front and hinder axles of the locomotive. And it will be easily seen that when the locomotive reaches such a point that the fore wheels are on one of the isolated rails, and the hind wheels on the other, the electric circuit (provided the drawbridge is closed) is completed through the magnet and the bell rings, indicating that it is safe to proceed; but if the drawbridge or switch is open the bell will not ring, for the electric circuit is not closed, and the conductor is warned to stop, or to proceed with caution. The means proposed for obtaining this important end are simple and not expensive, and the idea is certainly a very ingenious one-and it will be observed that the result of any failure in the apparatus is simply to excite the cautiousness of the conductor the safety signal cannot be given unless everything is in order. This constitutes, in the opinion of the Committee, the very great merit of the contrivance. In practice, the difficulties which suggest themselves will be in perfectly isolating the rails, especially in low situations, or in very wet or icy weather; and secondly, the arranging the extre mities of the magnetic coil so that the current from the wire will pass through them. There can be little doubt that the grease on the well-oiled axle of a locomotive will prevent the passage of an electric current of such feeble intensity; and if it did not, it would pass through the pedestals and iron work of the engine to the other axle, and thus escape the magnetic circuit; but the avoidance of this objection will probably be easy; and the simplicity of the apparatus, and importance of the result to be obtained thereby, recommend Mr. McRea's invention to a practical trial. As soon as these objections were proposed to the inventor, he suggested a mode of obviating both of them, by terminating one end of the magnetic coil on a rod projecting downwards from the cow-catcher, the other on a rod projecting similarly from the hinder frame of the engine, and setting the insulated rails on the middle of the track, where they can easily be completely insulated. It would also be advisable that a signal be given to the switch or drawbridge tender, to prevent the possibility of his opening the switch or bridge after the engine had passed the signal station, but before reaching the point of danger. At Mr. McRea has also proposed a modification of the apparatus for avoiding the collision of trains on a single-track road. the turn-out at each extremity of the part of the track on which the trains may meet, the insulated rails are prepared as before, but at each point the wire is provided with a "circuit-changer," as shown in the accompanying drawings; the battery has a double circuit, each including one of these "circuit-changers." The ordinary position of the "circuit-changer" is such that the current to which it belongs is interrupted. Now, the conductor of the train who first arrives at one end of the prepared track, shifts the "circuit-changer" by a simple motion, and thus passes a current from the distant station through his magnet, and the ringing of the bell indicates that he may proceed in safety. In proceeding, he leaves the circuit-changer in its new position, by which the circuit at that end is broken. If now, while he is on the doubtful ground, the other train arrives, and the conductor shifts the changer at that end, he can get no circuit, and consequently his bell is silent--for it will be seen by the drawing that the current must come from the far station, and that has been thrown out by the first train in passing. He must, therefore, wait. As the trains pass off the ground, they must stop to readjust the "circuit-changers" in their first position. It will be seen here, again, that any failure of the apparatus, or negligence in its adjustment, can only produce delay, and that provided the first conductor performs his duty a collision is impossible. These changes may, it is manifest, be easily made by the locomotive itself, if that be deemed desirable. The Committee therefore report that the invention of Mr. McRea appears to present a simple and not expensive means of adding materially to the safety of railroad travelling, and that it is in their opinion worthy of trial in practice, which is the only thing which can finally decide upon its utility; and they recommend that a description of the instrument be published in the Journal of the Institute. By order of the Committee. W. HAMILTON, Actuary." Art. IX.-THE GROVE ELECTRIC BATTERY. REMARKS ON BATTERIES-WARNING ΤΟ COMPANIES ΤΟ BE CAREFUL IN ADOPTING ANY NEW BATTERY-RULES FOR BUILDING AND KEEPING UP A GROVE BATTERY. THIS battery is in general use over America, though on a few lines the copper battery--commonly known as the Dutch battery-is in operation. Whether or not any other battery now known is superior to the Grove series, is a question that we are unable to decide. We do not advise any line to abandon a well-tried battery to enter the field of experiments. Nearly every telegrapher in the United States has invented an insulator, and many lines have been ruined forever by the sad experiments. Fortunately for the enterprise, there has been but little effort to change the battery. There is a feeling prevailing throughout the country, tending to encourage experiments, however, and we now timely warn the managements of lines to stand aloof from any untried battery. Let them be well tested, and thoroughly established as better than the Grove, before adopting them. That there will be devised a galvanic battery of equal powers and of less expense than pertains to the one now in use, we have not a doubt; but, that every one recommended will subserve the ends in view, we do not for one moment believe. Many of the managers of lines know but little as to batteries, and do not pretend to be experts in the science. They leave such questions to their operators, and unfortunately an occasional indiscretion brings with it sad results. In writing thus, we do not wish to be understood as uttering one word against those batteries mentioned in the present number. The battery proposed by Mr. Carpenter, of Rhode Island, has not been applied, and therefore it remains a question, requiring demonstration, as to its efficiency in telegraphing. The one proposed by Mr. Chester, of New-York, has progressed in experiment for some months, and has proved, thus far, quite successful. It has been put on a circuit form New-York to Boston, some two hundred and forty miles, but its application has been conjunc tively with the Grove battery at other places on the line. How it would work on a line with circuits of four and five hundred miles we know not, nor can we express any opinion about it. We hope it will answer, and if so, the economy in its use will be many thousands of dollars per annum. We can see nothing preventing its success; but electricity is an element of nature so little known, that facts cannot always be obtained by abstract reasoning-practical experiments are the sure tests. We do not know the constitutional parts of the battery proposed by Mr. Chester, and therefore cannot speak as to its cost further than he has seen fit to give in a preceding article. We have seen it operate and admire it very much, and earnestly hope it may succeed. In conversation with Dr. J. Lawrence Smith, at the Smithsonian Institute in Washington, we learned that a Smee battery would answer for telegraph purposes on short circuits, and with some alterations, might be made very serviceable. Instead of having platinized silver, lead, and various other less valuable metals, may be platinized, and thus a very cheap Smee battery can be made. In a few months, we feel confident, some plan will be devised to rid the lines throughout the country of much of the expense and trouble now incurred in the use of the Grove battery, either by the substitution of a new, |