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 considered the process to be "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 Bell 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. Emperor Pedro II of Brazil was the first person to buy stock in Bell's company, the Bell Telephone Company. One of the first telephones in a private residence was installed in his palace in Petrópolis, his summer retreat 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: Competitors As is sometimes common in scientific discoveries, simultaneous developments can occur, as evidenced by a number of inventors who were at work on the telephone. Over a period of 18 years, the Bell Telephone Company faced 587 court challenges to its patents, including five that went to the U.S. Supreme Court, but none was successful in establishing priority over the original Bell patent and the Bell Telephone Company never lost a case that had proceeded to a final trial stage. Bell's laboratory notes and family letters were the key to establishing a long lineage to his experiments.