2fi4 



Scientific Proceedings^ Roijal Dublin Societi/. 



the element, but by taking special pains to heat the tube as much as possible 

 by a Mekei! burner, and photograph the capillary tube just at the lower 

 bend, close to the bulb containing the chloride, I got a good pliotograph 

 showing a fair number of the calcium lines, and the bands in the red were 

 strongly developed. It is probable that by stronger heating similar photo- 

 graphs of strontium and barium might be obtained, though I did not succeed. 

 The band in the ultra-violet is due to chlorine. Strong bands are seen in 

 the orange and red, also from A 3600 to \ 4100, due, no doubt, to calcium 

 chloride. 



Principal Lines of Calcium. j 



Stkontium. 



Strontium chloride yields a spectrum in the vacuum tube with difficulty, 

 and only at the strongest heat of the Meker burner, when three lines 

 photograph well, these being the ultimate lines of the spark spectrum of the 

 element. The luminescence is occasionally a very deep carmine, and, as with 

 calcium and barium, it does not extend up the capillary tube. The strong 

 line at the extreme red is lithium, X 6708*2. The water-vapour and chlorine 

 bands are seen, and there do not appear to be any other bauds. 



The ultimate line of magnesium, A 2852-2, is seen, but not the fainter 

 pair seen in calcium. 



