SOLAR ECLIPSE OF AUGUST 29, 188G. 
The work expected from this instrument by the Committee of the Ptoyal Society 
was an examination of the spectrum of the inner corona immediately before and after 
totality, and a search for the bands of carbon during totality. The observations 
before and after totality were to serve as a test of the accuracy of Mr. Lockter’s 
theory concerning the concentric layers of the solar atmosphere, in which selective 
absorption is supposed to take place. It is important to know whether nearly the 
whole of the Fraunhofer lines are produced in the layer observed by Professor Young 
close to the photosphere in 1870, or whether they are due to the combined absorptive 
action of successive layers, each producing its own characteristic lines. If the latter 
hypothesis be the true one, then the layei’S nearer the Sun’s centre, being hotter than 
those outside them, should produce brighter lines. These, therefore, -would be the 
first to come into view as the eclipse approaches totality, and they would also be the 
most enduring after totality. Belonging, as they are supposed to do, to the inner 
layer, they should be short and bright, and not increase in length, but only in relative 
intensity, as the darkness became greater. The other lines, belonging to layers 
farther removed fi’om the Sun’s centre, would be invisible at first, owing to their want 
of intensity, but they would gradually come into view as the darkness increased, and 
always appear less brilliant and longer than those which preceded them. Immediately 
after totality the previous order would be, of course, reversed, the longest lines, 
which are also the faintest, disappearing first, and then the others, according to their 
length, leaving the shortest and brightest in view, until even these are at last over¬ 
powered by the returning light of the photosphere. In 1882 the Egyptian observa¬ 
tions had favoured this theory, and Mr. Turner was asked to repeat in 1886 the 
observations previously made in the F. region, wdiilst Father Perry watched the same 
phenomena in the region on the less refrangible side of h. Tlie plan adopted at Carriacou 
w’as that Lieutenant Helby should keep the slit of the spectroscope radial on the 
centre of the solar crescent for eight minutes both before and after totality, whilst 
Father Perry watched the changes in the bright line spectrum of the inner corona. 
To enable the assistant to point the telescope wuth very great accuracy, a cap with a 
white enamelled surface haxi been closely fitted to the slit, and on this cap two sets 
of parallel lines at right angles to each other had been most carefully ruled, the 
distances between the lines being one-tenth of the projected diameter of the solar 
disk. The cap could be fixed only in one position, so there was no possible chinger of 
one set of lines not being in exactly the same direction as the slit, and still less of the 
slit being partially covered. A clear image of any visible corona was thus secured, 
and the assistant could see perfectly whether the required portion of the image fell 
upon the slit. 
The remaining work expected from this instrument was a search during totality for 
the two principal bands of the carbon spectrum. In 1883 Professor Tacchini had 
thought he glimpsed the carbon bands, and some few previous obseiwations rendered 
their existence in the coronal spectrum not improbable. It was evidently of very 
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