on WAVE-LENGTH TABLES OK THE 9FECTBA OF THE ELEMENTS. '.'>■'>] 



Report of the Committee, consisting of Efcofessor Sir H. E. Koscoe, 

 Mr. J. X. Lockyeh, Professors Dewar, Wolcott GtIbbs, Livklvg. 

 SCHUSTEB, cmd W. N. HabTLET, Captain Ajsnky, cmd Dr. Matcbwat.t. 

 Watts (Secretary), appointed for the pv rpose of preparing a nevj 

 series of Wave-length Tables of the Spectra of the Elements, 



Ix the following tables are brought together the chief measurements of 

 the wave-lengths of the bright lines constituting the spectra of the 

 elements, and of certain compounds, so far as they are known to the 

 Committee or have proved accessible. The measurements are given in 

 ten-millionths of a millimetre (or tenth-metres), and are based upon the 

 measurements of the Fraunhofer lines by Angstrom for the visible rays, 

 and the extension of the same series of measurements into the ultra- 

 violet portion of the spectrum made by Cornu and other observers. It 

 will be well to bring together here these fundamental values of wave- 

 length of the chief solar lines. The small corrections indicated at pao-e 

 29 of Angstrom's Memoir, ' Le Spectre Normal du Soldi. ' have been 

 applied to his numbers — but they are uncorrected for the dispersion of 

 air. Hence the numbers in the tables represent wave-lengths in air of 

 760"" pressure at Upsala, and 16° C. temperature. The numbers taken 

 from Thalcn's ' Determination des Longeurs d'Onde des Raies Metalliques ' 

 in the same way have had applied to them the necessary small corrections 

 to bring them into harmony with the numbers finally adopted by 

 Strom as ' Valeurs definitives ' (pp. 2o and '■'> L-32). 



Feaujthopbb Links 



(Ke) . . J19-8 



(Fe) . . . 3727-0 



(Fe) . . . 3680-6 



( l", double) . 3439-8 



(Fe a: Ti) . . 3369-2 



(Fe) . . . 3284-9 



(FeftCa) . . 3179-0 



(Fe, double) . 3144-3 



B, (Hi,double). . 3100-6 i .,..,, 



(Fe, triple) . . 3099-5/ <51wo 



(Fe) . . . 3046-4 



I Fe, double) . 3019-7 



(Fe) . . . 2994-3 



(Fe) . . . i".U7-s 



The following symbols are employed in the tables to indicate the 

 character of the lines : 



s b that the line is sharply defined. 



n denotes that the. line is ill-defined or nebulous. 



b denotes a band, the position of the brightest part being given. 



I»" denotes a band sharply defined on the least refracted side, and fading away 



towards the blue'. 

 b denotes a band sharply defined on its more refracted side, and fading away 



towards the red. 

 '• denotes that the line is continuous. 

 d denotes that tlie line is discontinuous, or a ' short ' line. 

 r denotes that the line is frequently ' reversed/ 

 A number within parentheses, thus : (3091-9), means that while a line in this- 



position has been observed, no new measurement of wave-length was made 



— the wave-length being quoted from another observer. 



The intensities of the lines are expressed upon an ascending scale 

 from 1 to 10 ; 1 being the feeblest and 10 the brightest. 



