Modified Batchelder insulator

Varieties.

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TELEGRAPH INSULATORS.—At a stated monthly meeting of the Franklin Institute, February 24th, Dr. Turnbull called the attention of the meeting to the very great importance of proper insulation of the metallic wires of the electro-magnetic telegraph. He exhibited two new forms of insulators. The first was a modification of the form designed by J. M. Batchelder, Esq., of Boston, but omitting the use of iron, and being composed of flint, quartz, and feldspar, very compact, thoroughly vitrified on the surface, was equal to the best forms of glass insulators and much stronger; it is in the form of a cap, with a ridge for the purpose of fastening the wire, and an inverted edge, so as to divert the rain downward and prevent it from entering the inside of the cap. He remarked that even this form of insulator is defective, and the moisture settles upon it, and this acts as a carrier of the electricity to the ground. A still further modification of this apparatus is desirable, so as to give the surface of the insulator a downy covering, to cause the moisture to remain in isolated dress upon it; this Mr. Batchelder is endeavoring to accomplish. He has also produced a change by heat, &c, in the best electric substances known, namely, caoutchouc, so as to render it impervious to moisture, heat and rapid decomposition, and fit it for insulating caps for the tops of posts.

The composition is of a dark color, and in the form exhibited, has a ringing noise when struck. Subjected to water at 212 deg. it did not soften; strong sulphuric acid had no action upon it; even pure nitric acid did not destroy its elasticity, while it completely altered a piece of pure caoutchouc, converting it into a mass of brown color, which, when pressed between the finger, falls to powder. The only change noticed was its color, which was yellow instead of black. When placed in the dame of gas it burned with freedom, giving off scintillations as if combined with metallic oxide, and leaves a polished surface, while ordinary caoutchouc liquid, when burned, produced a pyro-oil, which stains the fingers, so that it has all the qualifications of a good insulating substance, being an electric not affected by a heat of 212 deg., nor altered by acids, and not liable to decomposition.—Journal Franklin Institute.

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