Showing their identity with two lines in the Solar Spectrum. 5 
The wave-lengths of the two gallium lines determined from these are as 
follows :— 
Reversed lines, Plate 1v., ; 4172°214 and 4033-125. 
Lines in Plate v., . : : . 4172°214 and 4033-120. 
With the stronger line the numbers vary between 4172°210 and 4172-216, and 
with the weaker line between 4033°117 and 4033°128. 
The relative intensities of the two gallium lines are the same in the oxy- 
hydrogen flame, the arc (bright and reversed lines) and spark spectra ; and they 
are fairly represented on Rowland’s scale by 1 and 00. 
We consider the wave-lengths determined from the reversed lines to be more 
accurate than those determined from the bright lines in Plate v. In the latter 
the gallium lines and closely adjacent iron lines overlap. We therefore adopt 
4172°214 and 4033°125 as the wave-lengths of two lines in the spectrum of gallium 
which have been observed in various substances examined by us. 
There are two lines, 4172°296, Fe, and 4033°224, Fe-Mn, which are so closely 
adjacent that we have not been able to distinctly separate them from the gallium 
lines, even when working on spectra of the second order, though the ends of the 
two lines can be observed with the microscope quite distinctly. By working ina 
clearer atmosphere, with a higher order of spectrum and a narrower slit, it may 
be possible to distinctly separate two Fraunhofer lines of these wave-lengths. 
The evidence that gallium is contained in the sun is of the following 
character :— 
1. This element, in minute proportions, is extraordinarily widely distributed in 
the crust of the earth, in felspar, mica, basalt, iron ores, and aluminous minerals 
generally. It is also commonly found, as we have ascertained, in pumice and 
volcanic dust from New Zealand and Krakatoa; thus proving its presence in the 
interior of the earth. 
2. Gallium is a common constituent of iron meteorites, associated with nickel 
and cobalt.* 
3. The lines of gallium, both in the are and spark spectra of a solution of 
gallium chloride, show that the less refrangible is the stronger line, and that their 
relative intensities are represented by 1 and 00 on Rowland’s scale. 
4. In the are spectrum of gallium, these two lines are very easily reversed. 
5. The wave-lengths of the gallium lines, 4172-214 and 4033-125, correspond 
with two lines in the solar spectrum, one of which has been assigned to aluminium 
by Rowland, the wave-lengths of which are 4172-211 and 4033-112. 
As owing to the chemical properties of gallium oxide—its separation from 
alumina and other sesquioxide bases is extremely difficult, and requires a very 
* Scientific Proc. Roy. Dub. Soc., vol. viii. (N.S.), Part vi., p. 705. 
TRANS. ROY. DUB. SOC., N.S. VOL. VII., PART I. CG 
