EFFECT OF PRESSURE UPON ARC SPECTRA. NICKEL. 



243 



The existence of another group is indicated by the occurrence of five lines which are 

 displaced towards the violet. The amount of their displacement is approximately the 

 same as that of Group IB. if no allowance be made for the fact that all the measure- 

 ments were made at 10 atmospheres pressure. 



We may designate the nickel groups as follows : 



Group 0, d = - 4'3 xlO-"X 3 . 

 IA., d = + 2'5 xlCT 14 A :! . 

 IB., d = + 5'0 xlO- 14 A 3 . 

 II, d = +1075xlO- n X 3 . 



In the above groups several lines are included whose displacements under pressure 

 have not been measured ; their classification is based upon their general behaviour and 

 resemblance to lines whose grouping lias been ascertained. 



In addition to the two main groups, further sub-division is possible as inspection of 

 the photographs will show. In the following table are given those lines which bear 

 close resemblances to one another; it may be of service in the resolution of the nickel 

 spectrum into the usual spectrum scries. 



Line. 



2 



3 



4 



7 



10 

 11 

 14 

 19 

 31 



39 

 42 

 43 



46 



63 

 65 

 68 

 81 



A. 



3453-64 

 58-59 

 61-78 

 93-10 



3510-47 

 15-17 

 24-65 

 66-50 



3619-52 



I 



TABLE X. 



All strong linos. 



Very greatly broadened under pressure. 



Their broadening is nearly symmetrical. 



All are strongly reversed under pressure. 



The reversals are placed nearly symmetrically upon the bright lines. 



2, 3, 4 are very similar. 



10, 11, 14 are very similar. 



19, 31 are very similar. 



It does not appear likely that 10, 11, 14, 19, 31 form a series, because there i 

 a break in the rate at which the breadth of the reversal increases with wave- 

 length. In the recognized iron triplets which have been examined there was 

 a regular decrease with wave-length. 



3664 24 1 Moderately strong lines. 



74-28 I Moderately broadened. 



88-58 f Unsymmetrically reversed, the reversal being on the violet of centre. 

 3722-63 J 39 and 42, 43 and 46 are more closely related. 



3775-71 

 83-67 



3807-30 

 58-40 



All strong lines. 



Greatly broadened under pressure. 

 Broadening nearly but not quite symmetrical. 

 Reversals strong and nearly symmetrical. 



The continuous increase in separation, in breadth and in width of reversal suggei 

 that these lines are related in some intimate way. 



All nebulous at atmospheric pressure. 

 }- All weakened under pressure and invisible at high pressure. 

 100 103 104, 110 have the appearance of converging series. 



