TABLE 179. 



STANDARD WAVE-LENGTHS, 



This table is an abridgment of the table published by Rowland (Phil. Mag. [5] vol. 36, pp 49-75). The first column 

 gives the number of the line reckoned from the beginning of Rowland's table, and thus indicates the number of 

 lines of the table that have been omitted. The second column gives the chemical symbol of the element repre- 

 sented by the line of the spectrum. The third column indicates approximately the relative intensity of the lines 

 recorded and also their appearance ; A" stands for reversed, d for double, ? for doubtful or difficult. The fourth 

 column gives tie relative " weights " to be attached to the values of the wave-lengths as standards. The last 

 column gives the values of the wave-lengths in Angstrom's units, i. e., in ten millionth* of a millimetre in ordinary 

 air at about 20-' C. and 760 millimetres pressure. When two or more elements are on the same line of the table 

 it indicates that they have apparently coincident lines in the spectrum for that wave-length. When two or more 

 lines are bracketed it means that the first one has a line coinciding with one side of the corresponding line in the 

 solar spectrum and so on in order. Lines marked A(o) and A(iw) denote lines due to absorption by the oxygen 

 or water vapor in the earth's atmosphere. The letters placed in front of some of the numbers in the first column 

 are the symbols of well-known lines in the spectrum. The footnotes are from Rowland's paper. 



SMITHSONIAN TABLES. 



172 



