180 Mr. J. N. Lockyer on Spectrum Analysis. [Dec. 12, 



the last four years has consisted in the elimination of the effects of 

 impurities. I am therefore aware of the great necessity for caution 

 in the spectroscopic examination of various substances. There is, 

 however, a number of bodies which permit of the inquiry into their 

 simple or complex nature being made in such a manner that the 

 presence of impurities will be to a certain extent negligable. I have 

 brought this subject before the Royal Society at its present stage in 

 the hope that possibly others may be induced to aid inquiry in a 

 region in which the work of one individual is as a drop in the ocean. 

 If there is anything in what I have said, the spectra of all the ele- 

 mentary substances will require to be re-mapped — and re-mapped 

 from a new standpoint ; further, the arc must replace the spark, and 

 photography must replace the eye. A glance at the red end of the 

 spectrum of almost any substance incandescent in the voltaic arc in a 

 spectroscope of large dispersion, and a glance at the maps prepared 

 by such eminent observers as Huggins and Thalen, who have used 

 the coil, will give an idea of the mass of facts which have yet to be 

 recorded and reduced before much further progress can be made. 



In conclusion, I would state that only a small part of the work to 

 which I have drawn attention is my own. In some cases I have 

 merely, as it were, codified the work done by other observers in other 

 countries. With reference to that done in my own laborator}^ I may 

 here repeat what I have said before on other occasions, that it is 

 largely due to the skill, patience, and untiring zeal of those who have 

 assisted me. The burthen of the final reduction, to which I have 

 before referred, has fallen to Mr. Miller, my present assistant ; while 

 the mapping of the positions and intensities of the lines was done by 

 Messrs. Priswell, Meldola, Ord and Starling, who have successively 

 filled that post. 



I have to thank Corporal Ewings, R.E., for preparing the various 

 diagrams which I have submitted to the notice of this Society. 



December 19, 1878. 



W. SPOTTISWOODE, M.A., D.C.L., President, in the Chair. 



The Presents received were laid on the table, and thanks ordered for 

 them. 



The following Papers were read : — 



