SCIENTIFIC TRANSACTIONS 



OF THE 



ROYAL DUBLIN SOCIETY. 



VOLUME VII. 



I. 



A DETERMINATION OF THE WAVE-LENGTHS OF THE PRINCIPAL LINES 

 IN THE SPECTRUM OF GALLIUM, SHOWING THEIR IDENTITY WITH 

 TWO LINES IN THE SOLAR SPECTRUM. By W. N. HARTLEY, F.R.S., 

 AND HUGH RAMAGE, A.R.C.Sc.I. 



(Plate I.) 



[Eead Makch 16, 1898.] 



It having been shown by us* in the examination of a number of minerals, such as 

 felspar, mica, basalt, pumice from Krakatoa, volcanic dust from New Zealand, 

 iron ores, aluminous minerals, and of meteoric iron and meteoric dust, that 

 gallium is a common constituent, present only in small proportion, it seemed of 

 interest to determine whether traces of this element are to be found in the solar 

 spectrum. 



In order to test this matter by a more accurate investigation than is possible 

 with ordinary instruments, we have been glad to avail ourselves of the very kind 

 offer of assistance made by Dr. W. E. Adeney, Curator of the Royal University 

 of Ireland. He has afforded us the means of photographing spectra with the fine 

 Rowland concave grating of twenty-one and a-half feet radius which has been 

 mounted in the Physical Laboratory of tlie University. The instrument was 

 adjusted so that we could photograph on one plate, 19^ inches long, the region, 

 in the second order, between wave-lengths 3990 and 4500. Cadet "Lightning 

 plates " were used, and they were developed with hydroquinone. 



* Proc. Eoyal Society, vol. 60, pp. 35 and 393. Trans. Chemical Society, 1897, pp. 533 and 547. 

 Journal Iron and Steel Institute, 1897, No. ii., p. 182. Scientific Proc. Eoy. Dub. Soc, vol. viii. (N.S.), 

 Part Ti., No. 68. 



TEAH8. EOT, DUB. SOC, N.S. TOL. TU., PABT I. B 



