All About Inventions and Discoveries
The Romance of modern scientific and mechanical Achievements

i6o All About Inventions Serbian engineer residing in the United States—Dr. Michael Idvorsky Pupin. Some years ago this scien- tist discovered a means of increasing the self-induc- tion of the circuit, thereby maintaining the strength of the currents or waves sent over the wire. His device was a coil, described as a " loading coil,” which was introduced into the circuit. But the coil, as then devised, was cumbersome and expen- sive, since thick copper wire was used. Yet the coil was adequate to demonstrate the value of the invention, and forthwith it was purchased by Mr. Vail, who handed it over to his own engineers for im- provement. As a result of the combined efforts it was found possible to reduce the size of the coil and to use wire of hair-like thinness. These coils are introduced at intervals of eight miles along the 3,400 miles of the transcontinental wire. In their con- struction 27,300 miles of fine wire, four-thousandths of an inch in diameter, were used. The opening of the transcontinental system was historic in more senses than one. It was inaugurated by Dr. Graham Bell, who was seated at the New York end, while Mr. Watson was at the San Fran- cisco terminus. During the opening ceremony the original transmitter which Dr. Bell had used on that historic afternoon of March 10th, 1876, was coupled up, and the first sentence sent over a telephone wire : “ Mr. Watson, come here, please ; I want you,” was repeated. Although the transmitter had been improved out of recognition during the passage of forty years, the words were reheard with perfect distinctness, though not quite so loudly, by the inventor’s old colla-