The peculiar electric current that these young pathfinders had to deal with is perhaps the quickest, feeblest, and most elusive force in the world. It is so amazing a thing that any description of it seems irrational. It is as gentle as a touch of a baby sunbeam, and as swift as the lightning flash. It is so small that the electric current of a single incandescent lamp is greater 500,000,000 times. Cool a spoonful of hot water just one degree, and the energy set free by the cooling will operate a telephone for ten thousand years. Catch the falling tear-drop of a child, and there will be sufficient water-power to carry a spoken message from one city to another. Such is the tiny Genie of the Wire that had to be protected and trained into obedience. It was the most defenceless of all electric sprites, and it had so many enemies. Enemies! The world was populous with its enemies. There was the lightning, its elder brother, striking at it with murderous blows. There were the telegraphic and light-and-power currents, its strong and malicious cousins, chasing and assaulting it whenever it ventured too near. There were rain and sleet and snow and every sort of moisture, lying in wait to abduct it. There were rivers and trees and flecks of dust. It seemed as if all the known and unknown agencies of nature were in conspiracy to thwart or annihilate this gentle little messenger who had been conjured into life by the wizardry of Alexander Graham Bell. All that these young men had received from Bell and Watson was that part of the telephone that we call the receiver. This was practically the sum total of Bell's invention, and remains to-day as he made it. It was then, and is yet, the most sensitive instrument that has ever been put to general use in any country. It opened up a new world of sound. It would echo the tramp of a fly that walked across a table, or repeat in New Orleans the prattle of a child in New York. This was what the young men received, and this was all. There were no switchboards of any account, no cables of any value, no wires that were in any sense adequate, no theory of tests or signals, no exchanges, NO TELEPHONE SYSTEM OF ANY SORT WHATEVER. As for Bell's first telephone lines, they were as simple as clothes-lines. Each short little wire stood by itself, with one instrument at each end. There were no operators, switchboards, or exchanges. But there had now come a time when more than two persons wanted to be in the same conversational group. This was a larger use of the telephone; and while Bell himself had foreseen it, he had not worked out a plan whereby it could be carried out. Here was the new problem, and a most stupendous one--how to link together three telephones, or three hundred, or three thousand, or three million, so that any two of them could be joined at a moment's notice.