OP ARTS AND SCIENCES. 405 



lines as it was possible to measure. The liuiits of the group were 

 assumed arbitrarily, aud the lines numbered from 1 to 37 inclusive. 



o 



To avoid confusing lines thus designated witli those called by Ang- 

 strom ij, b.^, ig, b^, it will be necessary to write these figures above 

 the line, as ¥, b^'^, etc. It might be noticed here that each of the 

 lines b^ and 6^^ has a faint " companion" or component just outside the 

 limits adopted, aud therefore not shown. Wave-lengths can be read 

 directly from the chart, to the tenth part of a tenth-metre, by estimat- 

 ing to tenths upon the scale, and suHixing the three (igures thus ob- 

 tained to 51 : — for instance, the wave-length of b* will be 



5164.3 tenth metres. 



The relative intensity aud character of the lines are represented as 

 faithfully as possible ; though it has been found exceedingly difficult to 

 give any very good idea of the peculiar blurred or burred appearance 

 so noticeable in the lines b^, b.^, and b^. 



