or of some improved arrangements connected with the known science.

Many gentlemen have peculiar plans for maintaining the Grove battery. We give below the manner of building and renewing it, at one of the principal offices on a line of which we were acting as President, deeming it about the most economical mode in the premises. EDITOR.

BATTERY-KEEPER.-The battery-keeper shall have charge of the battery of each line, and see to its construction according to the following system, and to be in readiness at the required. working hour in the morning.

Before using zines in battery, they should be well amalgamated with crude mercury. The mercury penetrates immediately if zines are first immersed in water strongly acidulated with muriatic, sulphuric, or other acids.

To the water in tumblers, add about 1-30 part sulphuric acid for ordinary use. To prevent freezing, and to remove the oxide which may form very rapidly from having strong ground connection on line, add a larger proportion of acid. The excess of oxygen corrodes zincs, and soon destroys the efficiency of the battery.

When the battery is once set at work, the following rules shall be observed in taking care of it :

Empty acid of porous cups into a vessel every night, and keep closed until morning. Remove zincs from the tumblers, and set them in water slightly acidulated (with sulphuric), to remain over night; if not bright in the morning, make them so.

In the morning, add a porous cup full of nitric acid, for every ten cups used in battery, having first poured out a portion of the old, if there be an excess.

To make the battery still stronger, add more pure nitric, and make water in tumblers stronger with sulphuric.

The water in tumblers should be changed twice a week.

MR. TAL. P. SHAFFNER:

NEW-YORK, April 28th, 1854.

Dear Sir:-A specimen of the nitric acid sold by the American Telegraph Confederation was given to me a few days since, for qualitative examination. I subjected it to the usual chloride of barium and nitrate of silver tests, for the presence of sulphuric or muriatic acids, without detecting a trace of either. I then compared its strength (by the alkalimeter) with that of the best commercial acid I could get at a drug store, (price 18c.), and found it only 5 per cent. weaker. Baumer hydrometer gave 42°, specific gravity 1.414.

Very respectfully, &c.,

CHARLES T. CHESTER.

THE importance of good insulation is not likely to be overestimated. It is, in fact, the prime and essential requisite of a successful telegraph line. Without it, however well a line may be constructed and operated, it can never attain to permanent prosperity.

The

line was built at an expense quite adequate to the construction of as perfect a line as any in the Union. From the start, it worked very irregularly-never during a continuous rain-and its unfortunate reputation was soon thoroughly established. It lingered on in this way, never half paying expenses, till it was sold under the hammer for debt-the original stockholders realizing a dead loss. The purchasers re-insulated the line, and made it comparatively reliable, and it soon improved in reputation, and secured a profitable and constantly increasing business.

This, with slight variations, is the substantial history of many telegraph lines. Whatever other defects of materials or construction may have contributed to these untoward results, the

great leading and ruinous defect in all these instances has been imperfect insulation. No one conversant with the history of telegraph lines will fail to confirm this statement, by instances occurring under his own observation. That these evils should have been so general heretofore, is not perhaps remarkable, when we recollect that contractors and builders of lines have often been ignorant of practical telegraphing, and have had no other interest in the lines but to make the most out of their contracts.

Latterly, there has been decided improvement in this respect; but we have not yet reached perfection, nor even a very near approximation to it. Those who make the most constant use of the telegraph do not trust to it in rainy weather. They have learned by experience that it is then always slow, and often quite uncertain. This is not a mistaken prejudice. It is a fact, that many lines-perhaps the majority-do not work successfully through ordinary storms, on account of defective insulation.

What is the best insulator is, therefore, a question of some importance. The earthen, wooden, and other insulators, whose non-conducting capacity is wholly superficial, and easily destroyed, have come to be correctly appreciated, and we need not enlarge upon their defects.

The plain glass is a good insulator while it continues whole, but it is fragile, and needs to be often replaced. An experienced line-repairer estimates that, while passing regularly over one hundred miles of line, put up with large glass insulators, he finds ten or more broken at every trip; showing that the line, though constantly attended to, can never have a perfect insulation without a more durable insulator.

Glass, protected by an iron cap, is extensively used, and has its advantages. But I find a growing distrust of this insulator among experienced telegraphers, on account of the difficulty of determining when they are defective. In many cases defects can only be detected by a close examination of each insulatora slow and expensive process. I confess I prefer the smallest and poorest plain glass insulator, to the best iron-capped insulator I am acquainted with.

The White Flint Insulator, invented by E. B. Elliott, Esq., of Boston, has recently been brought into favorable notice by the medals and diplomas conferred upon the inventor, by the Crystal Palace Exhibition in New-York, and the Massachusetts Mechanics' Fair in Boston. The following figures represent some of the most approved patterns of this insulator.*

The figure at the head of this article gives a front view of the heaviest pattern. The other figures give sectional views of the different patterns, and the numerals show the measurements, in inches, of the sockets, etc.

The great excellencies of this insulator are, that the material is anti-porous, is vitrified throughout, and is as perfect an insulator as glass, while it has many times the strength of the best flint glass, so that it needs no iron protection. Indeed, you may strike it against the ordinary iron-capped insulator, and the iron and glass will be shivered to fragments, while the White Flint is uninjured. Bullets fired against the outer surface are flattened, without fracturing the insulator. Of course it can be broken. But it is unquestionably very tough, and not liable to be broken under ordinary circumstances. In this respect it is a superior insulator. The interior corrugations prevent the accumulation of continuous lines of moisture in damp weather.

This insulator is cheaper than any iron-capped insulator of equal strength, and although the first cost is rather more than glass, it is in the end much cheaper, because its durability obviates the expense of frequent renewal, and the still greater loss consequent upon the imperfect working of lines in rainy weather. I have not seen one upon the line so broken as not to remain a good insulator. None of No. 1 have been broken, and a few only of the smallest pattern, that had been frequently assailed with missiles, had lost fragments of the rim, but were still whole for half an inch or more below the groove, to which the wire is attached. Line-repairers also mention as an advantage, that the contrast of the white flint with the wire shows at a distance the exact position of the line and the wire, making it easier to examine the line while passing over it rapidly. This is specially important to lines built upon railroads, which must, of necessity, be examined with great rapidity when interruptions occur.

If I were about to build a new line, I would use No. 2 of the above on a pin of hard pine. This would afford an insulation practically perfect, and as cheap as any good insulation can be. I should expect to see a line thus insulated, working well in weather when most lines entirely suspend operations, or are worked with extreme difficulty.

The use of wooden pins instead of iron, besides the additional insulation, would also avoid the frequent splitting of poles by lightning, from which many lines suffer severely in the hot

season.

For the reasons imperfectly alluded to above, and others that will be obvious to the candid reader, I prefer the White Flint Insulator to any other, and I invite the attention of telegraphers to its merits. It seems to me to possess all the essential requisites-perfect insulation, strength, durability, and economy.

Boston, April 22.

J. E. H.