It was writing upon a tablet that is like a bastard-file, with a steel-pointed stylus. Each slight projection makes a hole in the paper, and then the stencil idea begins again. Something has been previously said of the difficulties attending the making of the filament for the incandescent light. It is a little thing, smaller than a thread, frail, delicate, sealed in a bulb almost absolutely exhausted of air, smooth without a flaw, of absolutely even caliber from end to end. The world was searched for substances out of which to make it, and experiments were endlessly and tediously tried; all for this one little part of a great invention, which, like all other inventions, would be valueless in the want of a single little part. There are hundreds, an unknown number, of inventions in electricity in this country whose authors are unknown, and will never be known to the general public. The patent office shows many thousands of such in the aggregate. Many useful improvements in the telephone alone have come under the eye of every casual reader of the newspapers. These are now locked up from the world, with many other patented changes in existing machines, because of the great expense attending their substitution for those arrangements now in use. All the principles--the principles that, finally demonstrated, become laws--upon which electrical invention is based, are old. It seems impossible, during the entire era of modern thought, to have found a new trait, a development, a hitherto unsuspected quality. Tesla, in some of his most wonderful experiments, seems almost to have touched the boundaries of an unexplored realm, yet not quite, not yet, and most likely absolute discovery can no farther go. To play upon those known laws--to twist them to new utilities and give them new developments--has been the work of the creators of all the modern electrical miracles. There is scarcely a field in which men work in which the results are not more apparent, yet all we have, and undoubtedly most we shall ever have, of electricity we shall continue to owe to the infant period of the science.