480 
ME, J. N OEM AN LOCKYEE ON SPECTEUM-ANALYSIS 
the lines, but in retaining their characteristics in the memory until a record of length, 
thickness, and brilliancy could be placed on paper. Further, I have determined that 
when it is a question of mapping the various characteristics of the lines which the new 
method reveals in the spectrum of the vapour of a metal in the electric arc, and not the 
position only, on an average ten lines an hour is the progress made. At this rate the 
work I have proposed to execute would be interminable. I have therefore attempted 
to bring in the aid of photography. 
But there was another reason. I have long had cause to think that many, if not all, 
of the coincidences which Angstrom, Thalen, and others have chronicled — coincidences 
which made the allocation of the Fraunhofer lines so difficult and, worse still, doubtful 
^-had no real physical existence, but resulted from impurities ; and it seemed to me that 
this question could be at once settled by confronting photographs of the spectra of those 
vapours in which the coincidences have been recorded ; because if the coincidences were 
due to impurities, the lines would be longest and thickest in the spectrum to which they 
really belonged. 
The portion of the spectrum on which the attempt has at present been made is that 
from H to F. I may add that I have grounds for supposing that the least refrangible 
part of the spectrum thus left unrecorded is, in the case of the metallic elements, the least 
important one to study, and that I am making arrangements for photographing the 
part of the spectrum more refrangible than H. 
I have been fortunate enough not only to devise a very convenient method of thus 
confronting spectra, but of applying it under almost the best possible conditions, since, 
by the kindness of Dr. Frankland, I have been permitted the use of a room in his 
laboratory, where I have been enabled to photograph the spectra of the vapours of the 
solar metals, confronting these spectra with the solar spectrum and the spectra of other 
allied metals on the same plate. 
As this branch of the research has necessitated the use of a battery of 30 or 40 cells, 
it would have been impossible to carry it on in my dwelling-house, where all my 
previous work has been conducted. 
The construction of a Table of all the named Fraunhofer lines, showing the length 
and thickness of the lines of the metallic vapours to the absorption of which they are 
probably due, has also been taken in hand. This Table enabled me, before the photo- 
graphic work was commenced, to allocate upwards of 50 lines in the solar spectrum, 
which had, I presume, been overlooked by Angstrom and Thalen. 
It is, however, incomplete, inasmuch as I was not in a position to record the lengths 
of all the lines of iron and titanium with the induction-spark ; and since the photo- 
graphic work has been going on such a flood of light has been thrown on the true origin 
of so many of the unnamed Fraunhofer lines, that the Table in question may be said 
to be already useless for the part of the spectrum from H to F. 
This Table was made as a preliminary to the construction, on a much larger scale than 
Angstrom’s, of a new photographic map of the part of the spectrum from H to F, in which 
