58 



UK. \V. GEOFFREY DUFFIELD ON THE 



at atmospheric pressure or under 50 atmospheres pressure, it is the line K, which is 

 to be expected as it is the stronger of the two. This is, however, not in agreement 

 with an observation made by LIVEINO, quoted by MUGGINS* in a paper entitled 

 " The Relative Behaviour of the H and K Lines of the Spectrum of Calcium," who 

 states that when calcium occurs as an impurity in a carbon arc the H line sometimes 

 appears by itself. 



The negatives that had previously been taken in the region X 4000 to X 4600 were 



examined for the calcium line at 4226, but only a trace of it was discovered, and 



then only in the comparison spectrum, on photographs at 10 and 20 atmospheres. It 



is unfortunate that the H, K, and <j lines were not upon the same plate, as they might 



have contributed to our knowledge of the origin of these lines under different 



conditions of density. The conclusion arrived at by HUGGINS,* arid later by 



BARNES, t that the H and K lines are produced by a rare vapour of calcium and the 



;/ lines by dense vapour is not confirmed by the fact that H and K appear far more 



readily at +5 atmospheres than they do at atmospheric pressure. But possibly the 



above results are vitiated by the localisation of an impurity, as has already been 



suggested. 



TABLE II. 



Region A. X 3550 to X 4000. 



5 atmospheres 

 10 

 15 

 20 

 25 



30 atmospheres 



40 



50 



60 



80 



100 atmospheres 



150 



175 



200 



Region B. X 4000 to X 4600. 



5 atmospheres (2) 

 10 (2) 



20 



40 atmospheres 



60 



80 



100 atmospheres 



150 



200 



Region C. X 4600 to X 5 100. 



5 atmospheres 

 10 

 20 



40 atmospheres 



60 

 80 



100 atmospheres 

 200 



The Photographs: (1) Region Investigated. -The investigation of the gold 



^tttz^*** to / h 4raph these ^ 



* 



necessary to make ex^res in 





