ON THE TOTAL SOLAR ECLIPSE OF AUGUST 29, 1886. 
325 
The backs of the cameras employed could be tilted so as to have a larger portion of 
the spectrum in focus at once. It would be wortli while to determine by calculation 
the best shape of the camera lenses in order that the foci of the different rays shall be 
as much as possible in a straight line. An achromatic lens is not as good for the 
purpose as an ordinary lens, but a combination might be found which would give 
better results than the ordinary lenses. 
3. Results. 
The general appearance of the spectrum of the corona, as shown on the plate 
exposed during the whole of totality in the spectroscope described above as No. II., 
is given in Plate 9, fig. 1. It has a streaky appearance, consisting of a series of 
bands stretching from the ultra-violet into the green, and is crossed by the bright lines 
of corona and prominences. The horizontal bands are parallel to the dust lines, but 
they must be chiefly due to the different brightness of the portions of the corona cut 
by the slit. This is shown by the fact that they are wider and more diffuse than the 
dust lines shown on the reference spectrum, and that we are able to recognise in the 
photograph of the corona itself the brighter portions cut by the slit. A few dust lines 
do actually appear, but can be easily distinguished. Fig. 5, p. 326, shows the section 
of the corona cut by the slit. The left-hand part of the drawing is a tracing of the 
streamers in the corona. The line A A' is the line along which I had intended to place 
the slit. It is parallel to the declination circle, and tangential to the western limb of 
the Sun. It was, however, impossible to place the slit accurately in the position 
aimed at, and I think that, for reasons presently to be mentioned, the slit really ran 
along the line BB'. It must have crossed one of the prominences, for the prominence 
lines are very strongly marked, and this prominence will allow us to fix exactly the 
position of the image on the slit. 
The right-hand part of the drawing gives the distribution of light and shade in the 
spectrum of the corona near the Solar line G reduced to the same scale as the outline 
of the corona. The images of. the prominence appear along the line marked P. If 
we go from this line towards the southern side we find, in the first place, a strongly 
marked band, due no doubt to those parts of the corona which are closely adjacent to 
the Sun’s limb. This band and the next are separated by an interval in which the 
photographic intensity is very small along the spectrum, and I believe that here the 
slit must to some extent have overlapped the image of the Moon. 
Next comes a band, marked (2) in the drawings, in which all corona lines appear 
very strongly. Here the slit must have crossed the most intense streamer of the 
Solar corona, as will be seen by comparison with Mr. Wesley’s drawing. The most 
southerly band (l) coincides with the section of another streamer. It was the light 
interval between (2) and (3) and the portion of this band (1) which induced me to 
fix on the line BB' as the most probable line of the slit. 
