est of the Atlantic. No striking gain in
knowledge, however, resulted. Important experiments were indeed made on
the heat of the corona with Langley's bolometer, but their upshot can
scarcely be admitted as decisive. They indicated a marked deficiency of
thermal radiations, implying for coronal light, in Professor Langley's
opinion,[581] an origin analogous to that of the electric
glow-discharge, which, at low pressures, was found by K. Angstrom in
1893 to have no invisible heat-spectrum.[582] The corona was
photographed by Professor Barnard, at Wadesborough, North Carolina, with
a 61-1/2-foot horizontal "coelostat." In this instrument, of a type now
much employed in eclipse operations and first recommended by Professor
Turner, a six-inch photographic objective preserved an invariable
position, while a silvered plane mirror, revolving by clockwork once in
forty-eight hours (since the angle of movement is doubled by
reflection), supplied the light it brought to a focus. A temporary
wooden tube connected the lens with the photographic house where the
plates were exposed. Pictures thus obtained with exposures of from one
to fourteen seconds, were described as "remarkably sharp and perfectly
defined, showing the prominences and inner corona very beautifully. The
polar fans came out magnificently."[583]

The great Sumatra eclipse left behind it manifold memories of foiled
expectations. A totality of above six minutes drew observers to the Far
East from several continents, each cherishing a plan of inquiry which
few were destined to execute. All along the line of shadow, which, on
May 18, 1901, crossed Reunion and Mauritius, and again met land at
Sumatra and Borneo, the meteorological forecast was dubious, and the
meteorological actuality in the main deplorable. Nevertheless, the
corona was seen, and fairly well photographed through drifting clouds,
and proved to resemble in essentials the appendage viewed a year
previously. Negatives taken by members of the Lick Observatory
expedition led by Mr. Perrine[584] disclosed the unique phenomenon of a
violent coronal disturbance, with a small compact prominence as its
apparent focus. Tumbling masses and irregular streamers radiating from a
point subsequently shown by the Greenwich photographs to be the seat of
a conspicuous spot, suggested the recent occurrence of an explosion, the
far-reaching effects of which might be traced in the confused floccular
luminosity of a vast surround