SOLAR ECLIPSE OF AUGUST 29, 1886. 
;j5‘j 
Since tlie observations were taken I have frequently wished that my equatorial 
had been supplied with clockwork, which would have enabled me to dispense with 
the aid of an assistant for fixing, in each case, the position of the slit. I have not 
any reason to doubt but that the gentleman who so kindly aided me on this occasion 
did his duty as perfectly as could be expected; but it is not such an easy matter for 
one who has had only a few days’ acquaintance with the slow-motion rods of an 
equatorial to keep the slit of a spectroscope on any precise point of a celestial object. 
The strength of the wind and the imperfections of the slow-motion rods added in 
the present instance to the difficulty of following the Sun exactly with the R.A. rod, 
and of changing the N.P.D. as required. I am forced to the conclusion that the time 
lost by the unaided observer in placing the slit of his spectroscope would be more 
than compensated by the security he would feel, that he was viewing exactly the 
desired point of the object. Without clockwork this is not practicable ; but I should 
never think of again attempting eye observations with a spectroscope during a total 
eclipse without a clock to drive my ec[uatorial, and then, if a grating was used, I 
should certainly dispense with any assistant at the telescope. 
The two main questions to be answered by the spectroscopic observations at 
Carriacou were : (1.) Does the absorption, which produces the Fraunhofer lines, take 
place mainly in a single layer of the solar atmosphere, or in concentric layers ? 
(2.) Does carbon exist in the corona ? As far as the above results may afford any 
satisfactory evidence on these two points, I should be inclined to say that the 
difference in the length of the lines observed before totality on the less refrangible 
side of h seems somewhat to strengthen the view that the absorption takes place in 
concentric layers. And the search for carbon tells us that, if present, its spectrum 
was not strong enough in 1886 to make any appreciable effect upon the retina, when 
the eclipsed Sun was viewed through so powerful a diffraction spectroscope as that 
used a.t the island of Carriacou. It may, perhaps, be established, b}^ later observa¬ 
tions, that the intensity of the carbon spectrum varies in each eclipse, and may have 
some direct connection with the amount of solar activity. 
I should mention in conclusion that the diameter of the solar imao;'e on the slit 
plate of my spectroscope was 20 millimetres, the width of slit used jorn 
its effective length The dispersion was sufficient to enable me to see bg and 6^, 
very distinctly separated. 
Subjoined are the Sketches of the Coronal Streamers with explanatory notes by 
Lieutenant Commander J. Masterman, R.N. (Plate 11), and Mr. F. W. Osburn, 
KN. (p. 362). 
