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 wire as slender as a mosquito's leg, he could swing the needle back toward the middle of the scale and get the exact reading.

At another balance a scientist was snipping shreds from a long ribbon of gold. I was allowed to hold it in my hand, and though its curator explained deprecatingly that it was only 999.5 thousandths pure, it seemed pure enough for all my purposes. It is wonderful stuff, soft enough to tie in knots and yet so tough that it is very difficult to cut with heavy shears. That strip of about sixty ounces was worth well over $1200—and they didn't even search me when I left the building. "Proof gold," it seems, which is 1000 pure, is worth $40 an ounce, and all the proof gold used for scientific purposes in this country is refined in the Philadelphia Mint. The assistant assayer showed me lots of nice little nuggets of it in a drawer. Almost every drawer he opened contained enough roots of evil to make a newspaperman happy for a year.

In a neat little row of furnaces set into a tiled wall I was shown some queer little cups heating to 1700 degrees in a rosy swirl of fire. These little "cupels," as they call them, are made of compressed bone-ash and are used to absorb the baser metals in an alloy. Their peculiar merit is that at the required temperature they absorb all the copper, lead or whatever other base metal there may be and leave in the cup only the gold and silver. Then the gold and silver mixture is placed