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 IV., . . 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, Fo-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 in a 

 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 arc 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 arc 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. EOT. DUB. SOC, N.S. VOL. VII., PAET I. Q 



