Gilbert's patent shackle ball insulator is not novel.

Nothing New Under the Sun.

I notice in your journal, dated the 11th January, a description of "Gilbert's Patent Shackle Ball Insulator," and beg to point out, as an illustration of the adage that there is nothing new under the sun, that a precisely similar article was in use in India some 22 years ago.

They were known as "testing balls" or "earthenware circuit breakers," and were introduced by Lieut. Shepherd, R.E., then in the Telegraph Department, to afford a means of interrupting the circuit, without cutting the line wire, for testing purposes, or for inserting the wires leading into an office. They are illustrated in the accompanying sketch, which is copied from the standard diagrams of the Department. There is a sample of the article, known as pattern No. 3,796, deposited at the India Store Depot, London, with the usual specification.

Mr. Gilbert's method of using these insulators differs from ours, but the idea is precisely the same. They are still in use in India, but not to any large extent, owing to their low insulation.

P. V. Luke,

Officiating Director, Indian Telegraphs,

Construction Branch.

Calcutta, February 12th, 1889.

[We are much indebted to Mr. Luke for such an interesting account of the doings in India so many years ago.—EDS. ELEC. REV.]