230 
bands are generally not coincident with any part of the band, 
sometimes being less and sometimes more refrangible. Thus 
the broad band in the flame-spectrum of calcium named Ca /3, 
is replaced in the spectrum of the intense calcium-spark by 
five fine green lines, all of which are less refrangible than 
any part of the band Ca /3 ; whilst in place of the red or 
orange band Ca a, three more refrangible red or orange lines 
are seen. The total disappearance in the spark of a well 
defined yellow band seen in the calcium spectrum at the 
lower temperature, was strikingly evident. "We have assured 
ourselves by repeated observations that, in like manner, the 
broad bands produced in the flame-spectra of strontium and 
barium compounds, and especially Sr a, Sr /3, Sr 7 , Ba a, 
Ba /3, Ba 7 , Ba S, Ba e, Ba > 7 , disappear entirely in the spectra 
of the intense spark, and that new bright non-coincident lines 
appear. The blue Sr 8 line does not alter either in intensity 
or in position with the alterations of temperature thus 
effected, but, as has already been stated, four new violet 
lines appear in the spectrum of strontium at the higher 
temperature. 
If, in the present incomplete condition of this most 
interesting branch of inquiry we may be allowed to express 
an opinion as to the possible cause of the phenomenon of the 
disappearance of the broad bands and the production of the 
bright lines., we would suggest, that at the lower temperature 
of the flame or weak spark, the spectrum observed is pro- 
duced by the glowing vapour of some compound , probably 
the oxide, of the difficultly reducible metal ; whereas, at the 
enormously high temperature of the intense electric spark 
these compounds arc split up, and thus the true spectrum of 
the metal is obtained. 
In conclusion, we may add that in none of the spectra of 
the more easily reducible alkaline metals (potassium, sodium, 
lithium) can any deviation or disappearance of the maxima of 
light be noticed on change of temperature. 
