The result, then, is this.  The smallness, the length of period, and therefore delicacy, of the instruments at the physicist’s disposal have until lately been simply limited by the behavior of silk.  A more perfect suspension means still more perfect instruments, and therefore advance in knowledge.

It was in this way that some improvements that I was making in an instrument for measuring radiant heat came to a deadlock about two years ago.  I would not use silk, and I could not find anything else that would do.  Spun glass, even, was far too coarse for my purpose, it was a thousand times too stiff.

[Illustration:  FIG. 5.]

There is a material invented by Wollaston long ago, which, however, I did not try because it is so easily broken.  It is platinum wire which has been drawn in silver, and finally separated by the action of nitric acid.  A specimen about the size of a single line of silk is now on the screen, showing the silver coating at one end (Fig. 5).

As nothing that I knew of could be obtained that would be of use to me, I was driven to the necessity of trying by experiment to find some new material.  The result of these experiments was the development of a process of almost ridiculous simplicity which it may be of interest for me to show.

The apparatus consists of a small crossbow, and an arrow made of straw with a needle point.  To the tail of the arrow is attached a fine rod of quartz which has been melted and drawn out in the oxyhydrogen jet.  I have a piece of the same material in my hand, and now after melting their ends and joining them together, an operation which produces a beautiful and dazzling light, all I have to do is to liberate the string of the bow by pulling the trigger with one foot, and then if all is well a fiber will have been drawn by the arrow, the existence of which can be made evident by fastening to it a piece of stamp paper.

In this way threads can be produced of great length, of almost any degree of fineness, of extraordinary uniformity, and of enormous strength.  I do not believe, if any experimentalist had been promised by a good fairy that he might have anything he desired, that he would have ventured to ask for any one thing with so many valuable properties as these fibers possess.  I hope in the course of this evening to show that I am not exaggerating their merits.

[Illustration:  FIG. 6.]

[Illustration:  FIG. 7.]

In the first place, let me say something about the degree of fineness to which they can be drawn.  There is now projected upon the screen a quartz fiber one five-thousandth of an inch in diameter (Fig. 6).  This is one which I had in constant use in an instrument loaded with about 30 grains.  It has a section only one-sixth of that of a single line of silk, and it is just as strong.  Not being organic, it is in no way affected by changes of moisture and temperature, and so it is free from the vagaries of silk which give so much trouble.  The piece used in the instrument was about 16 inches long.  Had it been necessary to employ spun glass, which hitherto was the finest torsion material, then, instead of 16 inches, I should have required a piece 1,000 feet long, and an instrument as high as the Eiffel tower to put it in.