t estimated at 340,000 miles. The substance emitting it
was thus present, though in a low state of incandescence. The continuous
spectrum was relatively strong; faint traces of the Fraunhofer lines
attested for it an origin, in part by reflection; and polarisation was
undoubted, increasing towards the limb, whereas in 1870 it reached a
maximum at a considerable distance from it. Experiments with Edison's
tasimeter seemed to show that the corona radiates a sensible amount of
heat.

The next promising eclipse occurred May 17, 1882. The concourse of
astronomers which has become usual on such occasions assembled this time
at Sohag, in Upper Egypt. Rarely have seventy-four seconds been turned
to such account. To each observer a special task was assigned, and the
advantages of a strict division of labour were visible in the variety
and amount of the information gained.

The year 1882 was one of numerous sun-spots. On the eve of the eclipse
twenty-three separate maculae were counted. If there were any truth in
the theory which connected coronal forms with fluctuations in solar
activity, it might be anticipated that the vast equatorial expansions
and polar "brushes" of 1878 would be found replaced by the star-like
structure of 1871. This expectation was literally fulfilled. No lateral
streamers were to be seen. The universal failure to perceive them, after
express search in a sky of the most transparent purity, justifies the
emphatic assertion that _they were not there_. Instead, the type of
corona observed in India eleven years earlier, was reproduced with its
shining aigrettes, complex texture and brilliant radiated aspect.

Concordant testimony was given by the spectroscope. The reflected light
derived from the corona was weaker than in 1878, while its original
emissions were proportionately intensified. Nevertheless, most of the
bright lines recorded as coronal[541] were really due, there can be no
doubt, to diffused chromospheric light. On this occasion, the first
successful attempt was made to photograph the coronal spectrum procured
in the ordinary way with a slit and prisms, while the prismatic camera
was also profitably employed. It served to bring out at least one
important fact--that of the uncommon strength in chromospheric regions
of the twin violet beams of calcium, designated "H" and "K"; and
prominence-photography signalised its improvement by the registration,
in the spectrum of one such object, of twenty-nin