5G2 
MR. J. NORMAN LOCKYER OR SPECTRUM-ANALYSIS 
ready and unfailing means of detecting cyclical changes, maps of the spectrum on a 
large scale must be constructed. 
By means of the photographic method described in the third Memoir of this series," 
and illustrated by its application to the mapping of the spectra of barium, calcium and 
strontium in the fourth,! I commenced in the year 1875 a new map of the solar spectrum 
° 
on four times the scale of Angstrom’s “Spectre Normal.” Specimens of this map in 
its earlier stages were laid before the Society, with a preliminary note, in November of 
that year. J After the presentation of this preliminary note, the construction of the map 
was carried on, until on January 10, 1877, I submitted to the Boyal Society a complete 
Memoir on the first part completed (W.L. 390-400 millionths millim.) with comparisons 
of the lines of 25 metals and complete tables, both of the solar and metallic lines. 
While this Memoir was in the hands of the referees, I received from my friend 
Mr. L. M. Butherfued, of New York, a magnificent reflection grating, with 17,280 
lines to the inch. This enabled me to attack the question of wave-lengths in a much 
more satisfactory manner than I had been able to do in the first instance. I therefore 
determined to reject my two years’ work and to do it all over again, in order, if 
possible, to introduce greater accuracy than the method of graphical interpolation, 
which I had been compelled to adopt in the first instance, had permitted. I therefore 
applied to the Boyal Society for leave to withdraw my paper, giving the above-stated 
reason for so doing, and at once received the required permission. 
I now beg to re-submit to the Society that part of the withdrawn Memoir which 
has reference to the spectrum of the sun, independently of the spectra of the metals. 
1 have determined to do this, not only because the reviewing of the wave-lengths of 
the metallic lines will take considerable time, but because during the time that the 
Memoir was in the hands of the Boyal Society, and that which has elapsed since I 
received it back, I have very nearly completed the survey of the whole of the metals 
for this region, so that the comparison can now shortly be given for the whole of the 
metallic elements united for this part. 
The section of the new normal spectrum comprises, as I have said, the Fraunhofer 
lines between W.L. 390-400 millionths millim. That portion of the map now in ques¬ 
tion is but a very small fraction of the whole region of the spectrum workable by 
photography, and my chief object in thus forwarding a fragment to the Boyal Society 
is to point out the necessity for, and to invite co-operation in, a work of such magnitude, 
and to publish full details of the methods I have found most effective for the use of 
those who may take up the research. For this reason, and because it may happen 
that a diffraction grating of the requisite brilliancy may not be forthcoming in all 
cases, I think it best to give a complete history of the production of the map, including 
that stage of graphical interpolation of wave-lengths which I have, by Mr. Butherfued s 
generosity, been able to supersede. 
* Phil. Trans., Yol. 1G4, Part II., p. 479. f Phil. Trans., Yol. 104, Part II., p. ,305. 
J Proc. Roy. Soc., 158, 1875. 
