aad of Simple Substances. 185 



Distance of the first chloride-of-calcium line from the 



starting-point 2*5 



Distance of the first iodide-of- calcium line from the y 



starting-point 

 Distance of the second chloride-of-calcium line from 



the starting-point 9 



~~ Distance of the second iodide-of-calcium line from the y -j-2'5' 

 starting-point 



from which y=l. 

 Hence the distance of the first iodide-of-calcium line would be 

 near the division 128*8, and the other near 126*3. The position 

 of the third line close to 128*8 might be directly determined 

 from the position of the line corresponding to it in the chloride- 

 of-calcium spectrum; it must be near 128*6. 



The observations of the fluoride-of-calcium spectrum do not 

 agree with the calculations. By calculation from the same equa- 

 tions as in the case of iodide of calcium, the distance, for instance, 

 of the two extreme lines of the fluoride of calcium would amount 

 to 9 degrees, while from observation it is 22 degrees. From 

 calculation from other equations these lines must be about 117 

 and 126; in the spectrum observed they are, on the contrary, 

 at 102 and 124. 



In the spectra of the haloid salts of strontium there is the 

 same behaviour as in those of calcium. 



Calculating from the distance of the extreme sharp lines of 

 bromide of strontium those of the corresponding lines of chloride 

 of strontium, taking the atomic weights of chloride of strontium 

 at 79*6, of bromide of strontium 123*8, the distance of these 

 bromide-of-strontium lines from one another being 6*5, the equa- 

 tion obtains (5.5 yg.g 



— f = tkttttj from which a; = 10*1. 

 on \ 123*8 



From the drawing x also = 10. 



Proceeding as with calcium, the starting-point calculated from 



both spectra gives the following equation : — 



Distance of the first chloride-of-strontium line from 



the starting-point y + 0'5 



Distance of the first bromide-of-strontium line from y 



the starting-point 



Distance of the second chloride-of-strontium line from 



_ the starting-point ?/-fl0*5 



Distance of the second bromide-of-strontium line from y -f 6*5 



the starting-point 



from which y = 0'9. 



Hence the starting-point lies near the division 138*4. 



Phil Mag. S. 4. Vol. 28. No. 188. Sept. 1864. O 



