EXPLANATION OF THE TABLES. 

 I. Wave-lengths. 



The wave-lengths given in the first column are on the Rowland system. The methods of identifi- 

 cation and the tables used have been treated in the preceding section. 



2. Intensity. 



This column is intended to give an approximate value of the intensity of the fines in the spark spec- 

 trum. The numbers are taken (with occasional modifications) from the tables of Exner and Haschek 

 for the spark spectrum as far as X4700, beyond which the intensities were estimated on the same scale 

 from my plates. Weak fines are graded " i " on this scale, but there is considerable variation in thestrength 

 of fines which are given this value. For the purposes of this paper, this grading of intensities is sufficient. 



3. Character of Separation. 



In this column is described the type of separation of each line when the n- and /(-components* are 

 combined, as is the case when the light of the spark is observed at right angles to the magnetic force- 

 fines without Nicol or other apparatus to separate the light vibrating in the two directions. Thus in 

 the reproductions the two portions of each spectrum showing the effect of the magnetic field should be 

 superposed to give the appearance of the fine as described in this column. 



The description gives the best judgment of the t}'pe of separation that can be made from the photo- 

 graphs. It must be considered in connection with the measured separation and widening of components 

 given in the columns for AX of the ti- and /(-components, and is usually made clear by these. Frequently 

 a supplementary remark is needed in the case of complex fines. 



A fine designated as triple has its one p- and two ?2-components of sufficient sharpness to give no indi- 

 cation that any of them are compound. Since the Zeeman components follow to some extent the general 

 character of the spectrum fine, when a fine is itself wide and diffuse, its components may be simple and 

 still not so sharp as those of fines which do not tend to diffuseness. The pro.ximity of the no-field fine on 

 the plate aids in the judgment of such cases, but some of them are uncertain at the best. The tendency 

 of some fines to reverse is very disturbing in this connection, since it is very difficult to obtain such fines 

 with really sharp components. Several iron lines between X3700 andX3900, which give wide reversals 

 in the arc and spark between iron terminals, can be made to show the Zeeman components also reversed, 

 by the use of a strongly condensed spark, so that a triplet appears as a sextuplet. To decide such cases 

 it was necessary to make special photographs, using much self-induction and also with carbon terminals 

 containing a little iron. The titanium photographs were also useful in this connection, since the titanium 

 used contained enough iron to give the stronger iron lines which appear with sharp components under 

 such conditions. 



The interrogation point is very freely used to indicate that the line is probably of the character given, 

 though not clearl}' shown to be so on the plates. The reason for doubt is usually given in the columns 

 for AX. Thus "triple?" means that the /(-component is sfightly widened so that it may not be simple, 

 but stiU the widening may be explained by the strength of the component or by the fact that the fine 



*n and /> are used throughout this paper as abbreviations of "normal" and "parallel." n denotes the Zeeman components 

 given by light vibrations in a plane at right angles to the lines of magnetic force, and /> those given by vibrations parallel to the force- 

 lines. The symbols correspond to the letters 5 and p regularly used in German publications. 



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