DR. W. M. HICKS: A CRITICAL STUDY OF SPFXTTRAL SKRIKS. 



whether the separations shown which differ from 2GO and 158, differ through a 

 satellite effect, or by successive collaterals of 15$ and 9cJ. For instance, putting 



158 = A', F 1 (oo)-F 1 (oo)(A') = 264 > 10, F,(oo) (-A') -F,(o>) = 256'39, 

 F a (oo)(-2A') -F a (oo)(_A') = 252-35, 



all which separations occur. In the lines now to be referred to, however, the 

 separations will he supposed to owe their defect from 260 to the satellite effect, and 

 thus treated it is clearly seen what an important r61e the A a term plays. 



Amongst the ultra-red lines observed by RANDALL* appear the following in wave 



numbers : 



(70) 9387-55 (4'4) 



(60)9547'08(l-82) 



1. <! (60) 9771-54 (-95) 



(5)9804787(1-5). 

 . (60) 9964*527 (3) 



159-93 



257-70 



159-76 



The figures in brackets before the numbers give intensities and those after the 

 estimated maximum errors. They clearly l>elong to the F cycle, and show within 

 error limits the normal separations. The run of the intensities would point to 

 negative values, with the first four respectively for / 31 , /, /, /, but also the 2nd, 

 4th and 5th might be f l} f 3 ,f 3 , whereby 9771 would not come in and the small 

 intensity for f a would be abnormal. On the first supposition, / = -9771 gives a 

 denominator 1752908 (23)-24'5 ' and / = -9804 =/ (-3). On the second, 

 / = 9547 gives a denominator 2'588000 (143) -79f Now 



or denominator of / 12 = 63 (ll96ri-36--36) -2S = 63A a -2A 



In the following the wave numbers of some sets of lines with their separations are 

 given. The low frequencies have been observed by LEHMANN and by HERMANN and 

 HOELLER. LEHMANN gives many weaker ones not observed by HERMANN and vice 

 versd. LEHMANN'S observations were earlier but are not nearly so accurate as those 



of the others. 



260-17 12896-53 



260-94 14402-09 158'63 1456072 



254-37 15157-63 157-88 15315'51 



2. 12636-36 



3. 14141-15 



4. 14903'26 

 14934'33 



5. 



16669-61 259-69 



16921-93 

 16929-30 



156-03 17077-96 



'Ann. d. Phys.,' 33, p. 745(1910). 



