658 
ME. J. NORMAN LOCKYER ON SPECTRUM-ANALYSIS. 
PLATE LII. 
Upper Half. 
Spectra of strontium salts in hydrogen with low-tension spark. 
A, spectrum of Sr I 2 . 
B, ,, ,, Si Bi 2 . 
C, „ „ Sr Cl 2 . 
D, ,, „ metallic strontium. 
Notes . — The lines in the red have been omitted, as they are difficult of observation, 
and the point is proved by the more refrangible lines. The bands are approximately 
laid down on the wave-length scale from readings of the scale of the Steinheil spectro- 
scope. 
Lower Half. 
Spectrum of the oxide of aluminium compared with the spectrum of the pure metal. 
A, spectrum of aluminium oxide. 
B, ,, „ aluminium. 
Notes . — The lines at W. L. 637L0 and 6344-5 are not shown; they have not been 
identified though seen by ThaLen. 
The spectrum A disappears in hydrogen. 
In air, with a low-tension spark, none of the metallic lines are seen, indicating that 
the oxide (Al 2 0 3 X) is not at all dissociated. 
The oxide spectrum is laid down on a wave-length scale from careful approximations 
to the lines of air, copper, and zinc. 
