Alexander Graham Bell
Later developments

On March 10, 1876, Bell used "the instrument" in Boston to call Thomas Watson who was in another room but out of earshot. He said, "Mr. Watson, come here – I want to see you" and Watson soon appeared at his side.

Continuing his experiments in Brantford, Bell brought home a working model of his telephone. On August 3, 1876, from the telegraph office in Brantford, Bell sent a telegram to the village of Mount Pleasant four miles (six kilometres) away, indicating that he was ready. He made a telephone call via telegraph wires and faint voices were heard replying. The following night, he amazed guests as well as his family with a call between the Bell Homestead and the office of the Dominion Telegraph Company in Brantford along an improvised wire strung up along telegraph lines and fences, and laid through a tunnel. This time, guests at the household distinctly heard people in Brantford reading and singing. The third test, on August 10, 1876, was made via the telegraph line between Brantford and Paris, Ontario, eight miles (thirteen kilometres) away. This test is said by many sources to be the "world's first long-distance call". It proved that the telephone could work over long distances, at least as a one-way call.

The first two-way (reciprocal) conversation over a line occurred between Cambridge and Boston (roughly 2.5 miles) on October 9, 1876. During that conversation, Bell was on Kilby Street in Boston and Watson was at the offices of the Walworth Manufacturing Company.

Bell and his partners, Hubbard and Sanders, offered to sell the patent outright to Western Union for $100,000, equal to $ 2,861,250 today, but it did not work (according to an apocryphal story, the president of Western Union balked, countering that the telephone was nothing but a toy). Two years later, he told colleagues that if he could get the patent for $25 million (equal to $ 789,310,345 today), he would consider it a bargain. By then, the Bell company no longer wanted to sell the patent. Bell's investors became millionaires while he fared well from residuals and at one point had assets of nearly $1 million.

Bell began a series of public demonstrations and lectures to introduce the new invention to the scientific community as well as the general public. A short time later, his demonstration of an early telephone prototype at the 1876 Centennial Exposition in Philadelphia brought the telephone to international attention. Influential visitors to the exhibition included Emperor Pedro II of Brazil. One of the judges at the Exhibition, Sir William Thomson (later Lord Kelvin), a renowned Scottish scientist, described the telephone as "the greatest by far of all the marvels of the electric telegraph".

On January 14, 1878, at Osborne House, on the Isle of Wight, Bell demonstrated the device to Queen Victoria, placing calls to Cowes, Southampton, and London. These were the first publicly witnessed long-distance telephone calls in the UK. The queen found the process "quite extraordinary" although the sound was "rather faint". She later asked to buy the equipment that was used, but Bell offered to make "a set of telephones" specifically for her.

The Bell Telephone Company was created in 1877, and by 1886, more than 150,000 people in the U.S. owned telephones. Bell Company engineers made numerous other improvements to the telephone, which emerged as one of the most successful products ever. In 1879, the company acquired Edison's patents for the carbon microphone from Western Union. This made the telephone practical for longer distances, and it was no longer necessary to shout to be heard at the receiving telephone.

Pedro II of Brazil was the first person to buy stock in the Bell Telephone Company. One of the first telephones in a private residence was installed in his palace in Petrópolis, his summer retreat forty miles (sixty-four kilometres) from Rio de Janeiro.

In January 1915, Bell made the first ceremonial transcontinental telephone call. Calling from the AT&T head office at 15 Dey Street in New York City, Bell was heard by Thomas Watson at 333 Grant Avenue in San Francisco. The New York Times reported:

On October 9, 1876, Alexander Graham Bell and Thomas A. Watson talked by telephone to each other over a two-mile wire stretched between Cambridge and Boston. It was the first wire conversation ever held. Yesterday afternoon, the same two men talked by telephone to each other over a 3,400-mile wire between New York and San Francisco. Dr. Bell, the veteran inventor of the telephone, was in New York, and Mr. Watson, his former associate, was on the other side of the continent.
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