. The Astrophysical journal. ed. The scale of the plates is A per mm. Table I presents the data for the metalHc arc between calciumpoles: TABLE I Pole-Effect at i Atmosphere. Calcium ElectrodesPositive minus Center IIN4 INs IIN5 1 IN6 Mean -| mm (28) — imti (21) mm (7) — mm (6) Negative minus Center IIX4 INs IINs IN6 Mean — mm (26) -f mm (27) — mm (7) mm (7) The numbers in parentheses indicate the number of measures averaged. The change of sign with the series is very striking, and appar-ently a continuous change in wave-length is indicat
. The Astrophysical journal. ed. The scale of the plates is A per mm. Table I presents the data for the metalHc arc between calciumpoles: TABLE I Pole-Effect at i Atmosphere. Calcium ElectrodesPositive minus Center IIN4 INs IIN5 1 IN6 Mean -| mm (28) — imti (21) mm (7) — mm (6) Negative minus Center IIX4 INs IINs IN6 Mean — mm (26) -f mm (27) — mm (7) mm (7) The numbers in parentheses indicate the number of measures averaged. The change of sign with the series is very striking, and appar-ently a continuous change in wave-length is indicated from onepole to the other. From a qualitative standpoint, the conclusions,we think, are quite definite, but on account of the unsteady 161 102 .l//.V()A CilXTRIBlTKiys AXD XOTKS conditions in the arc between calcium electrodes no great weightcan be attached to the numerical values. It is noteworthy that in the case of the calcium arc the shift ingoing from the center to the positive jH)le is opposite to that o u u. —IN6 Fig. I obtained in going from the center to the negative pole. As hasbeen observed by Goos and by St. John and Babcockr this is notthe case with the lines of the d and e groups in the spectrum of iron,where the shift in going from the center of the arc to the positivepole is in the same direction, though of a smaller amount, as thatfound in going from the center of the arc to the negative John and Babcock state that a longer exposure time is required ^ Aslrophysical Journal, 38, 141, 1913. -Ibid., 42, 231, 1915. MINOR CONTRIBUTIONS AND NOTES 163 at the center of the arc than at either pole in order to secure Unesof the same strength. We had noted that a longer exposure wasrequired at the negative pole than at the center of the arc, and alonger exposure at the center than at the positive pole, in the case ofthe subordinate series lines of calcium. We therefore projectedthe image of our calcium arc on the slit of a quartz bo
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