602 
MR J. NORMAN LOCKYER ON THE 
The spectrum of' a large prominence, No. 13 (fig. 9) at various heights from the 
photosphere, is shown in Table II. This prominence appears in all the African photo¬ 
graphs taken during totality,- and in some of those taken out of totality. In order 
that the changes of intensity of the various lines may be separated from the effects due 
to varying exposures, the individual observations are arranged in groups according to 
the exposure of the photographs. The total number of lines is much smaller than in 
the case of the two metallic prominences, but somewhat similar variations of intensity 
are noticeable. 
The spectrum of the chromosphere at different heights can also be partially 
investigated in the eclipse photographs. A considerable arc of chromosphere was 
photographed in the African Negative, No. 21 (Plate 11). The photograph was taken 
about ten seconds before the end of totality, so that the lower reaches of the solar 
atmosphere within 1,660 miles of the photosphere were hidden. The bright arcs 
accordingly represent the spectrum of the chromosphere above that height. None of 
the photographs give us any information as to the spectrum lower down until we 
come to the jiart very near to the base which, as already explained, is shown at the cusp 
in Photograph 22 (Plate 13). The complete spectrum of the base of the chromosphere 
is given in Table I., and in Table III. the lines common to the outer part of the 
chromosphere and to the base are brought together for comparison. 
Most of the lines become relatively brighter as the base of the chromosphere is 
approached, but some become dimmer. Further reference to these changes will be 
made later. 
The changes in the spectrum of a prominence in passing from the top towards the 
base are illustrated in Plate 14. Spectra a, b, and c represent the spectrum of 
Prominence No. 3 as it appears in the African Photographs Nos. 11,9. and 7 respec¬ 
tively, the first giving the spectrum of the upper part only, while the last shows the 
spectrum nearer the base. Accepting the time of commencement of totality in 
Africa as 2 hrs. 23 mins. 48 secs, by the deck watch, it is easily calculated that 
Spectrum 1 represents a part of the prominence 22"-26" (9,950 to 11,600 miles) above 
the photosphere ; Spectrum 2, 6"'7~8"'5 (3,000 to 3,800 miles) ; and Spectrum 3, 3' 7 
(1,660 miles) above the photosphere. Strip cl is the spectrum of the base of the 
chromosphere as represented by the cusp in the African Photograph No. 22. 
These enlarged spectra have been obtained by covering copies of the origiual 
negatives with tinfoil, leaving only narrow strips showing the prominence spectra, 
and giving them the necessary width by moving the photograph in a direction 
at right angles to the length of the spectrum, as described in a former paper." 
The want of exact coincidence of lines common to different horizons is due to the 
difficulty of obtaining enlargements on exactly the same scale. The difference in 
thickness of the same line in different photographs of a prominence is due to the 
varying sizes of the corresponding images of the prominence formed by the prismatic 
camera at different stages of the eclipse. 
* ‘ Phil. Trans.,’ 1893, vol. 184, A, p. 684. 
