short circuit would produce a violent ebullition. If a short circuit should be kept up for some time, decomposition would go on so rapidly, that zinc and acid would be destroyed faster than under the same circumstances in porous cell batteries, for the cell seems to act almost as a mechanical barrier to very rapid decomposition, and the chemical changes are more complex in batteries using two fluids-practically if the nitric acid battery, the sulphate of copper battery, and the Chester battery, were all set up in equal force, and a short connection with good conductors arranged for each, the last named would dispose of its zinc and acid earliest, and would give out first, -hence this battery is not well adapted for a local circuit, except in very judicious hands, where a full supply of material is furnished in proportion to the rapid waste.

Nor is it so well adapted to working a number of wires, for here in addition to the multiplied calls on its resources, the effects of cross fire among the wires is, also, to be added. These considerations point to the necessity of taking proper care of this battery, by simply keeping up a supply of new material in proportion to the waste, which indicates itself at all times. Should accident or very bad insulation produce an unusually rapid decomposition, then compensation should be made without delay, and the zinc surfaces examined. If neglected too long, like all other batteries, it proceeds to the work of self-destruction, but very slowly. First, the solution becomes changed from the quick, fierce acid, to the sluggish, dead sulphate. The unprotected zincs corrode, evaporation leaves white crystals of salt upon the plates, and the incrustation running up through itself by capillary attraction, fresh supplies of thick solution continue its encroachments till even the brass connections are attacked. The lifeless sulphate in some cell, weaker than the rest, becomes at length decomposed, and a deposit accumulates upon the negative plate. Thus, from neglect, the work of destruction commences from internal dissension. It would seem useless to caution against such negligence, but some curious instances have fallen under the writer's observation, where batteries set up properly, have been allowed to work five months without any renewal! Some inefficient operators have entertained the idea, that they would never require any further care, but in some mysterious manner supply themselves with acid in the same way that they did with quicksilver. It is desirable to use the best acid in charging. The difference of cost between the best and worst acids being about two cents per cup in a year. It has been very gratifying to witness the success of this battery, where it has been exclusively adopted and cared for in a systematic way.

(Z) Zine cylinder, (P C) Porous cup, (C) Copper cell with perforated copper chamber attached, (G) Glass.

Art. VIII-LOCAL BATTERY.

THE engraving represents one of the most popular arrangements for Local Battery now in use. It is known as "Chester's Local," and derives its peculiar construction from a great number of experiments, to secure the least objectionable form for a necessary appendage to the local circuit, and Morse Register. It is, in principle, Daniells' Battery; yet, Daniells' Battery in its highest power and best arrangement, would make a poor Telegraph Local Battery, the objections to it being, First, that the zincs could not be kept amalgamated without pulling the battery to pieces three or four times a day: Secondly, that the deposition of copper is very unequal, the solution of sulphate of copper becoming dense at the bottom, and thin at the top of the glass.

Experience has taught, that for the peculiar demand of a Local Telegraph circuit, if the plates are quite large, a full supply of sulphate of copper kept up, and its solution uniform in density, the zincs will, in some way, take care of themselves with no other excitant than warm water, and that the Battery will give out a steady and a full quantity current. It is presumed that just enough sulphuric acid oozes through the porous

cup to act as a gentle excitant to the zinc. But from whatever source it obtains its energy, the battery is sure to work long and well if these conditions are observed. The quantity of metal surface is secured in construction by the form of the copper and zinc plates-long hollow cylinders. Attached to the copper cell, is a chamber of the same metal, the floor of which is pierced with holes, and its cover is so contrived that it opens when a supply of sulphate of copper is poured in; thus preventing its falling into the porous cell, and attacking the zinc. The holes serve for access to the solution, which dissolves the fresh salt, and this being kept in the upper part of the glass, with a tendency to sink below, a uniformity of strength is secured. But as this battery in its operation deposits a large amount of copper upon the porous cup and copper cell, it is desirable to separate them occasionally, lest they may grow together and prevent circulation of the sulphate solution. The shape of the cell in relation to the glass, is made so that it can be spread out, and altered as the growth upon it increases, and yet be easily removed from the glass. Finally, the glass is made very large, and of great strength. These batteries supply a powerful local current of great quantity, continuing for about two weeks. The renewal consists in a supply of crystals of sulphate copper to the copper box, fresh clean water to the porous cell, and scraping off the thick black oxide that adheres to the zinc. When the zinc is entirely consumed, a fresh one is supplied with great ease, from the fact of requiring no binding screw attachment, the casting being so shaped as to fit easily into the brass clamp termination of the copper arm. The expense of this battery is about the same, or a little less, than other forms of Local Battery. The advantages secured, being, dispensing with poisonous fumes, and the necessity of daily attention.

Art. IX.-IMPROVED INSULATOR.

THE following engraving represents a section of the modern Shield Insulator, now very much used upon telegraph lines, and manufactured by Charles T. and J. N. Chester, of NewYork. It consists of the oak bracket (B), spiked to the pole (P). Over the rounded upper part of this bracket fits the glass (G), and this glass is protected by the tight fitting painted wooden shield (S).

The advantages of this insulator are that wood, a partial insulator, is substituted for iron, a conductor, as a bracket. The full benefit of the non-conducting properties of glass is

secured; but the glass surface, well known to collect moisture, is replaced by the painted wooden covering which, at the same time, serves to protect the glass from external violence. This Insulator is believed, by our first telegraph constructors, to be the very best in use.

Art. X.—T E L E G R A PH MANUAL.

ON many occasions we have been requested to give the details of manipulation practiced in the Morse system. Having our attention especially called to the subject, we insert the following extracts from a circular of the former President of the St. Louis and New-Orleans Line. Nashville and St. Louis were terminating points. The signals are explained under that head, and on reference to them the examples will be understood. It will be observed that the place addressed is first mentioned, to enable the instrument at the destination to be fairly in motion, so that the place from be not lost ere the register can indite the first writing.

The check abbreviations indicate the mode of passing messages from one line to another, the accounts of each being separate and distinct.

"In order to have system in all matters concerning this line, I have deemed it necessary to adopt RULES, regulating the manner of transmission and reception of messages between

offices, that there may be no confusion in the discharge of business.

In the promulgation of the codes pertaining to the working of this line, it is anticipated that those in the service will move every nerve to effect their fulfilment; and with zeal and fidelity commensurate with any exigency, promote the weal of the Company.

With the united aid of all, the strength of union will be realized, and glorious success will crown our efforts. Without the co-operation of the officers in command, hope for success will be idle.

The following remarks are given to illustrate the mode of business of the peculiar kind indicated, viz:

ST. LOUIS wants Nashville. The former re-adjusts his Magnet carefully, and finding no one writing, he calls Nashville thus, N N N N N A-observe the space. Call four or five times, then sign the signal of the office. Immediately after the sig. of office, adjust magnet. If no answer, call again, and repeat the call four or five times, pausing a reasonable time between calls for an answer. If St. Louis fails to get Nashville, after a space of a few minutes, the call should be resumed.

When Nashville hears his office called, he must wait for the signature A-then promptly answer thus: II N St. Louis will then commence and send his message, as illustrated by Example No. 1. If there is more than one message, then as Ex. No. 2.

The 3d and 4th examples illustrate their peculiar object. If Nashville receives the message, he answers thus: A O KN If Nashville does not, he answers thus: ARRN St. Louis will then repeat the message, until N gives the signals A O KN

After St. Louis sends, and adds as example No. 2, Nashville will then say, AOKGAN St. Louis will then resume sending, and, if the line works well, might send some half dozen or more, without Nashville answering AOKGAN to each message. Too much care cannot be taken in following these rules, to preserve uniformity and correctness in the discharge of business. The office signals of other lines must not be used, but the name in full, thus: G is signal for Louisville. G must not be used, but Louisville must be given in full.