ently the more expensive. When pure, platinum is as
soft as silver, but by the addition of iridium it becomes the hardest of
metals. The great difficulty in manipulating platinum is its excessive
resistance to heat. A temperature that will make steel run like water and
melt down fireclay has absolutely no effect upon it. You may put a piece
of platinum wire no thicker than human hair into a blast furnace where
ingots of steel are melting down all around it, and the bit of wire will
come out as absolutely unchanged as if it had been in an ice box all the
time.

"No means has been discovered for accurately determining the melting
temperature of platinum, but it must be enormous. And yet, if you put a
bit of lead into the crucible with the platinum, both metals will melt
down together at the low temperature that fuses the lead, and if you try
to melt lead in a platinum crucible, you will find that as soon as the
lead melts the platinum with which it comes into contact also melts and
your crucible is destroyed.

"A distinguishing characteristic of platinum is its extreme ductility. A
wire can be made from it finer than from any other metal. I have a sample
in my pocket, the gauge of which is only one two-thousandth of an inch,
and it is practicable to make it thinner. It has even been affirmed that
platinum wire has been made so fine as to be invisible to the naked eye,
but that I do not state as of my own knowledge. This wire my son made."

Mr. Baker exhibited the sample spoken of. It looked like a tress of silky
hair, and had it not been shown upon a piece of black paper could hardly
have been seen. He went on:

"The draw plates, by means of which these fine wires are made, are
sapphires and rubies. You may fancy for yourselves how extremely delicate
must be the work of making holes of such exceeding smallness to accurate
gauge, too, in those very hard stones. I get all my draw plates from an
old Swiss lady in New York, who makes them herself to order. But, delicate
as is the work of boring the holes, there is something still more delicate
in the processes that produce such fine wire as this. That something is
the filing of a long point on the wire to enable the poking of the end of
it through the draw plate so that it can be caught by the nippers. Imagine
yourself filing a long, tapering point on the end of a wire only one
eighteen-hundredths of an inch in diameter, in order to get it through a
draw plate that will br