. Carnegie Institution of Washington publication. THE AID OF THE ACHROMATIC FRINGES. 63 The current induced in the primary controls the objective of the vibration telescope, which thus moves with a lag a subject to (2) *=*'o sin (wt — a) and this may be modified by the resistance and inductance in the primary. The objective is, as stated, either mechanically or magnetically coupled with the vibrator on the interferometer in a way yet to be ascertained. Hence the vibrator displacements s are subject to an equation with a lag or lead (3) 5 = So sin (ut — in the absence of current in the secondar
. Carnegie Institution of Washington publication. THE AID OF THE ACHROMATIC FRINGES. 63 The current induced in the primary controls the objective of the vibration telescope, which thus moves with a lag a subject to (2) *=*'o sin (wt — a) and this may be modified by the resistance and inductance in the primary. The objective is, as stated, either mechanically or magnetically coupled with the vibrator on the interferometer in a way yet to be ascertained. Hence the vibrator displacements s are subject to an equation with a lag or lead (3) 5 = So sin (ut — in the absence of current in the secondary (R = »). Finally, the secondary, if carrying current, has its own lag or lead 7, depend- ing on the R, L, C, there inserted, and is thus subject to an equation (4) = s0 sin (at — 7) where 7 is essentially associated with /3, as seen in the preceding paragraphs. If we suppose the coupling implied in equation (3) to be uniform, the lag in equation (2) may be made obvious. In this way vibration figures were obtained, examples of which are given in figures 68 and 69. Calling the two nearly equal auxiliary self- inductions in the primary L and U (R= °° in the secondary), in the case of figure 68, the bands obtained in the absence of L or L' changed to ellipses of about the same range for either the L or L' insertion, and these to nearly horizontal bands when both L and L' were inserted. On removing the L+L' the first figure returned. In figure 69 the initial form (L = o) was an ellipse, changing to bands with but little differ- ence of phase between the L and 2L insertions. In all these cases the vibration figures were very large and very definite in the successions of their changes with L, however frequently repeated. The insertion of L (choking coil) naturally somewhat reduces i and there- fore the amplitude of the objective of the vibration telescope. It appears from figures 68 and 69 that at the same time the vibration of fringes is lessened and ceases practically und
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