erity on those contestants who miss the new gift by however little.
We shall, therefore, find that the principle of permutation, here merely
indicated, accounts in large measure for three cardinal facts in the
history of man: First, his leaps forward; second, the constant
accelerations in these leaps; and third, the gap in the record of the
tribes which, in the illimitable past, have succumbed as forces of a new
edge and sweep have become engaged in the fray.[6]

The interlacements of the arts of fire and of electricity are intimate
and pervasive. While many of the uses of flame date back to the dawn of
human skill, many more have become of new and higher value within the
last hundred years. Fire to-day yields motive power with tenfold the
economy of a hundred years ago, and motive power thus derived is the
main source of modern electric currents. In metallurgy there has long
been an unwitting preparation for the advent of the electrician, and
here the services of fire within the nineteenth century have won
triumphs upon which the later successes of electricity largely proceed.
In producing alloys, and in the singular use of heat to effect its own
banishment, novel and radical developments have been recorded within the
past decade or two. These, also, make easier and bolder the
electrician's tasks. The opening chapters of this book will, therefore,
bestow a glance at the principal uses of fire as these have been
revealed and applied. This glance will make clear how fire and
electricity supplement each other with new and remarkable gains, while
in other fields, not less important, electricity is nothing else than a
supplanter of the very force which made possible its own discovery and
impressment.

[Here follow chapters which outline the chief applications of flame and
of electricity.]

Let us compare electricity with its precursor, fire, and we shall
understand the revolution by which fire is now in so many tasks
supplanted by the electric pulse which, the while, creates for itself a
thousand fields denied to flame. Copper is an excellent thermal
conductor, and yet it transmits heat almost infinitely more slowly than
it conveys electricity. One end of a thick copper rod ten feet long may
be safely held in the hand while the other end is heated to redness,
yet one millionth part of this same energy, if in the form of
electricity, would traverse the rod in one 100,000,000th part of a
second. Compare next electricity wi