46 INFLUENCE OF A MAGNETIC FIELD UPON THE SPARK SPECTRA OF IRON AND TITANIUM. 



type, a great number of lines being classed as probable sextuplets which show as diffuse triplets with this 

 field. A field of considerably greater intensity will probably show these to be similar to most of the sex- 

 tuplets which are fully resolved here. The /"-components of those sextuplets which have been measured 

 are usually rather narrowly separated, while the two pairs of w-components are frequently almost blended. 



6. Septuplets. 



The prevailing type of septuplet has four w- and three /^-components, the two pairs of w-components 

 not usually being of the same intensity. When blended, the w-components give the "fringed" appear- 

 ance often noted in the "Remarks" column, in which case the weaker pair may be either inside or 

 outside. When the /^-components are not resolved, it is often difficult to distinguish this type from the 

 sextuplet, the difference depending on the existence of a central maximum in the widened />-component. 



7. OCTUPLETS. 



The typical octuplet has five n- and three /)-components, equally spaced. The outer w-components 

 are usually the stronger and the central one quite weak, so that when the three /^-components, if the 

 central one is the stronger, are superposed, as when the light is viewed across the lines of force without a 

 Nicol, the effect is to show five components of about equal intensity. Examples of such lines are 

 XX 3743.508, 3788.046, 5497.735, of iron, and 4281.530, 4527.490, 4544.864, of titanium. The last two 

 were given as septuplets in my former paper (51) on account of the weakness of the central -com- 

 ponent. Another arrangement is presented by the titanium line X 4308.081 which has three pairs of 

 M-components and two /j-components. 



8. Nonets. 



Good examples of lines having nine components are found in XX 3840.580, 4233.772 of iron, and 447 1 .408 

 4489.262, 4629.521 of titanium. These have each three pairs of H-components, the innermost pair being 

 strongest, and three /^-components. The type is probably rather common in both spectra, since many 

 fines classed as doubtful septuplets may have a weak outer pair of w-components, making a total of nine. 



9. More Complex Types. 



Lines having ten components are represented by XX 44 17. 884, 4471.017, and 5025.027 of titanium. 

 These are made up in each case of three pairs of n- and two pairs of /^-components. Eleven components 

 are shown by X 3888.671 of iron, which has a central w-component in adcUtion to the pairs of the ten- 

 component type. Several good examples of twelve-component lines are given by XX 3722.729, 3872.639, 

 5447.130 of iron and 4289.237 of titanium. These are all of similar structure, having four pairs of 

 w-components, the two inner pairs having the same separation as the two pairs of /^-components. While 

 twelve is the highest number of components which is measurable on my plates, the iron lines XX 4005.408 

 and 4132.235 are given as probably having thirteen components each. Five /^-components are almost 

 resolved in each case and the wide inner fringes for the w-components are estimated to consist of four 

 pairs. Many of the lines whose type is questioned without attempt to estimate the number of compo- 

 nents have probably as many as the most complex of those measured, and some of them possibly more. 



Good examples of almost all of these types of separation are present among the violet iron fines shown 

 in Plate III, which has the advantage of showing the w- and /^-components both separate and in combi- 

 nation, the latter spectrum being taken at right angles to the force-fines without the use of a Nicol prism. 

 Polarization by the grating reduced the intensity of the /(-component for this region of the spectrum, 

 as is shown by the relative weakness of the central component of triplets in the spectra lettered b, for 

 which the Nicol prism was not used. 



