Proceedings of the Physical Society Volume 20 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1907 Excerpt: ...This spectrum has been photographed with a large concave grating and the wave-lengths determined certainly to within a tenth of an Angstrom unit. The strong lines at the following points of the spectrum form a series analogous to the series obtained with the cadmium 480 series.-X differences. 5119-34 TO-fifl A V 6079-78..........' 6040-05 5001-57 4902-85.......... TM 4924-32.......... This we have called the first series. The wave-length differences are, in this case, much more nearly constant, and decrease progressively. The lines of this series are especially conspicuous in the magnetic rotation spectrum (PL I., fig. 1, c), hence I have mentioned it first; they appear in the fluorescence excited by the lead line 5001, as will be seen by reference to the chart. If now we try to fit one of the magnetic series to the cadmium 480 fluorescence series, we find that the third magnetic series coincides with it between 5019 and 5134, while in the violet region it coincides with the fourth magnetic set. I do not feel sure whether this peculiarity is due to slight errors in the determination of wave-lengths or not. I think not, however, for I have very carefully superposed the two negatives (cadmium fluorescence and magnetic rotation spectra), both taken with the same instrument, and find the same disagreement. We cannot be sure of anything, however, until the cadmium series has been photographed with the grating. During the coming year I expect to photograph the fluorescence spectrum excited by cadmium and zinc radiations with the large concave grating. It will then be possible to determine the wave-lengths of the lines to within a tenth of a unit. One of the most remarkable facts connected with the appearance of the lines of a series is that the distribution of en...