Brooks Improved Paraffine Insulator

Brooks' Improved Paraffine Insulator.

IN the last number of THE TELEGRAPHER, we gave an illustration of this insulator, as exhibited at the Paris Exhibition. This was the old form of construction, similar to that now used on two wires between New York and Pittsburg, and on many other lines in the State of Pennsylvania. This insulator has proved itself far superior to any other in use in this country, in confirmation of which fact we have the unanimous testimony of all the operators who have worked on the lines on which it is used.

But it would seem that nothing short of absolute perfection can satisfy Mr. BROOKS on the insulator question. Indeed he may almost be charged with being a monomaniac on the subject, to which he has devoted his attention for nearly twenty years. Not content with the success of his original invention, he has, within a few months, made such improvements in it, as to apparently leave nothing more to be desired.

In the annexed cut we give a sectional view of this improved insulator which shows clearly the manner in which its different parts are combined.

The iron hook or wire-holder of the usual form is sulphured into a narrow-mouthed, inverted flask or bottle, of blown glass, which is secured in like manner, into a cylindrical iron cup four or five inches in depth and about two in diameter. This is made slightly tapering towards the mouth, in order to prevent any danger of the weight of the wire tending to withdraw the hook and glass flask from within it. After a few days, when the sulphur has undergone its peculiar shrinkage, or crystallization, melted paraffine is poured in, thoroughly saturating and coating every part of the insulator, including the sulphur.

But the great improvement of this insulator over the old form consists in the addition of the bottle of blown glass. This substance possesses some peculiar qualities which Mr. BROOKS was the first to discover or at any rate to make known, and which render it vastly superior for insulating purposes to the cast or pressed glass which has been invariably employed heretofore. Mr. BROOKS accidentally discovered, in the course of his numerous experiments, that the inner surface of a vessel of blown glass possesses the property of repelling watery accumulations and causing them to unite in detached drops instead of covering the surface with a continuous film, as is the case with that portion of the glass which is brought in contact with the metallic mold, while in process of cooling. As will readily be seen, this is a fact of immense importance in its application to the use of glass for telegraphic insulation. It is well known that paraffine possesses the same quality in an eminent degree. Bearing in mind these facts, it will be seen that owing to the peculiar arrangement of the parts of this insulator, it offers an almost infinite amount of resistance to the escape of the electric current from the wire to the pole and thence to the earth. The current must pass first over the paraffine surface intervening between the stem of the hook and the interior surface of the glass bottle, and along this surface to its mouth, and thence along its exterior surface, and over another surface of paraffine, before it can reach the exterior iron case.

It might perhaps be supposed that a glass bottle thus situated would be liable to fracture, but such is not the case. The editor of the Franklin Institute Journal in speaking of this insulator, remarks that "those who are acquainted with the behavior of this substance (glass) under like circumstances will remember its wonderful tenacity. A glass tube rigidly clasped in a solid cap or covering is one of the most troublesome things to break out that has ever tried our patience. In fact these insulators will bear an immense strain without fracture, as we have seen by repeated experiments; or if they should in some cases yield, we know from analogy, that the crack would run around the bottle, and would thus do no harm to the insulation, which only fears a lengthwise fissure through which external moisture may penetrate. Brown earthenware, from its softer nature, crushes under like conditions, and is destroyed by a strain which the glass endures with perfect impunity."

It will be observed that the bell or umbrella form which is used in the majority of insulators is dispensed with. This is simply for the reason that it is better to let the rain-drops come nearer and pass by, than to stop them, even at a little distance, and by dashing them into fine spray, get them into the very condition best fitted for penetrating the mouth of the cup and bottle. The form adopted is also much stronger than the bell, and better adapted to resist external violence. The danger of injury from lightning has been guarded against in this insulator by making the distance less between the wire hook and the lower edge of the iron cup, than it is between the upper end of the stem and the top of the cup. As lightning always moves in the direction of the least resistance, it is evident that it will leap from the wire hook to the edge of the cup rather than at any other point.

The manufacture of this improved insulator was only commenced a short time since, and it has therefore not as yet come into extended use. One line of sixty miles in length, however, which we tested, showed no perceptible escape during a most severe storm, the wire working as clear as on a frosty morning in midwinter.

The new private line of HARRISON BROS. & CO., between New York and Philadelphia, uses this insulator, and we predict that the working of it will be found to more than verify all the statements we have made in regard to its merits.

It is not creditable to the enterprise or scientific knowledge of the managers of our American telegraph companies that this insulator, whose superiority over all others is an undisputed fact, should be used almost exclusively by railway and private lines, and almost entirely ignored by the different telegraph companies. We think they will have good cause in the future to regret the short-sighted policy that now prevails in relation to this and similar improvements.