th continuous light--as in the case of the solar
flames shining through our atmosphere--it derives a _relative_ gain in
intensity from every addition to the dispersive power of the
spectroscope with which the heterogeneous mass of beams is analysed.
Employ prisms enough, and eventually the undiminished rays of persistent
colour will stand out from the continually fading rainbow-tinted band,
by which they were at first effectually veiled.

This Janssen saw by a flash of intuition while the eclipse was in
progress; and this he realised at 10 A.M. next morning, August 19,
1868--the date of the beginning of spectroscopic work at the margin of
the unobscured sun. During the whole of that day and many subsequent
ones, he enjoyed, as he said, the advantage of a prolonged eclipse. The
intense interest with which he surveyed the region suddenly laid bare to
his scrutiny was heightened by evidences of rapid and violent change. On
the 18th of August, during the eclipse, a vast spiral structure, _at
least_ 89,000 miles high, was perceived, planted in surprising splendour
on the rim of the interposed moon. If was formed as General Tennant
judged from its appearance in his photographs, by the encounter of two
mounting torrents of flame, and was distinguished as the "Great Horn."
Next day it was in ruins; hardly a trace remained to show where it had
been.[516] Janssen's spectroscope furnished him besides with the
strongest confirmation of what had already been reported by the
telescope and the camera as to the continuous nature of the scarlet
"sierra" lying at the base of the prominences. Everywhere at the sun's
edge the same bright lines appeared.

It was not until the 19th of September that Janssen thought fit to send
news of his discovery to Europe. It seemed little likely to be
anticipated; yet a few minutes before his despatch was handed to the
Secretary of the Paris Academy of Sciences, a communication similar in
purport had been received from Sir Norman Lockyer. There is no need to
discuss the narrow and wearisome question of priority; each of the
competitors deserves, and has obtained, full credit for his invention.
With noteworthy and confident prescience, Lockyer, in 1866, before
anything was yet known regarding the constitution of the "red flames,"
ordered a strongly dispersive spectroscope for the express purpose of
viewing, apart from eclipses, the bright-line spectrum which he expected
them to give. Various delays, howe