beryl, orthoclase, and quartz. I was much surprised to find the last
mineral melt below the melting-point of platinum. I have, however, by me
as I write, a fragment, formerly clear rock-crystal, so completely fused
that between crossed Nicols it behaves as if an amorphous body, save in
the very center where a speck of flashing color reveals the remains of
molecular symmetry. Bubbles have formed in the surrounding glass.

Orthoclase becomes a clear glass filled with bubbles: at a lower
temperature beryl behaves in the same way.

Topaz whitens to a milky glass--apparently decomposing, throwing out
filmy threads of clear glass and bubbles of glass which break,
liberating a gas (fluorine?) which, attacking the white-hot platinum,
causes rings of color to appear round the specimen. I have now been
using the apparatus for nearly a month, and in its earliest days it led
me right in the diagnosis of a microscopical mineral, iolite, not before
found in our Irish granite, I think. The unlooked-for characters of the
mineral, coupled with the extreme minuteness of the crystals, led me
previously astray, until my meldometer fixed its fusibility for me as
far above the suspected bodies.

Carbon slips were at first used, as I was unaware of the capabilities of
platinum.

A form of the apparatus adapted, at Prof. Fitzgerald's suggestion, to
fit into the lantern for projection on the screen has been made for me
by Yeates. In this form the heated conductor passes both below and above
the specimen, which is regarded from a horizontal direction.

J. JOLY.