After what has been said in previous chapters, it will not seem so strange that Edison should have hundreds of dormant inventions on his hands. There are human limitations even for such a tireless worker as he is. While the preparation of data for this chapter was going on, one of the writers in discussing with him the vast array of unexploited things said: "Don't you feel a sense of regret in being obliged to leave so many things uncompleted?" To which he replied: "What's the use? One lifetime is too short, and I am busy every day improving essential parts of my established industries." It must suffice to speak briefly of a few leading inventions that have been worked out, and to dismiss with scant mention all the rest, taking just a few items, as typical and suggestive, especially when Edison can himself be quoted as to them. Incidentally it may be noted that things, not words, are referred to; for Edison, in addition to inventing the apparatus, has often had to coin the word to describe it. A large number of the words and phrases in modern electrical parlance owe their origin to him. Even the "call-word" of the telephone, "Hello!" sent tingling over the wire a few million times daily was taken from Menlo Park by men installing telephones in different parts of the world, men who had just learned it at the laboratory, and thus made it a universal sesame for telephonic conversation.