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secure a circuit from Philadelphia, but was unsuccessful for the same reason.

On July 11, 1876, Graham Bell varied the shape of the iron armature by attaching to the membrane a thin disk of Tagger's iron, almost as large as the membrane. The next day he gave one of these telephones to Sir William Thomson. It is said that during the trip home the armature became bent, and useless in that condition. Nevertheless, Sir William used it to illustrate to the members of the British Association for the Advancement of Science how Graham Bell's telephone was the most marvelous of all the wonderful exhibits he had seen in America.

Graham Bell continued his experiments in improving the telephone, and finding that the large iron disk was far superior to the small armatures previously used, he concluded to dispense with the membrane altogether. This he did in October, 1876. On fastening a thin disk of steel in front of the electromagnet, conversation was carried on more easily than ever before. Referring to this improvement, Mr. Storrow said:

Perhaps the most important contribution which Mr. Bell made towards improving speaking telephony, after the great conception and original instrument of his first patent, consisted in the wonderful sensitiveness and quickness of operation which he introduced into the instrument of the second patent, in consequence of the conviction which he reached by study, thought and experiment, that by so proportioning and combining all his parts as to sacrifice absolute strength to absolute quickness, he could obtain the best results; and then his innumerable experiments led him to the surprising discovery that a piece of sheet iron was much quicker and more faithful in following the delicate changes required for speech than the most delicate membrane is.

Nine years later the commissioner of patents, under date of March 3, 1885, wrote:

Bell's patent was issued on the 17th of March, 1876. At the Centennial Exposition, held at Philadelphia that year (1876), he exhibited his telephone, and it was adjudged by such eminent scientists as Professor Henry, Sir William Thomson, of England, and Professor Gray, one of the contestants herein, to be a success, and the world recognized Bell as the first inventor of a speaking telephone. The indications are that it was not until the promised reward for so important a public service became visible that his claim of priority was called in question by any of the parties to this interference.

That all the efforts of the several contestants who had attempted to produce a speaking telephone were failures seems clear from the record: that Bell was the first to give to the world the art of transmitting articulate speech, and the apparatus by which it could be successfully practised, was substantially conceded tor a long period after his success in that behalf was placed beyond doubt. Whether or not these several contestants had the instrumentalities and appliances at that time from which success might have been realized if those instrumentalities had been better understood is of little consequence. The history of their experiments is a history of recorded failures.

 

III. Devising the Telephone Exchange System

Thirty years ago this summer the annual meeting of the British Association for the Advancement of Science was held in Glasgow,