The Astrophysical journal . rtical axis so that a considerable part ofthe spectrum could be brought into focus at one time. The mounting of the instrument was arranged as in the diagram(Fig. 1). Usually the source of light studied was placed directly infront of the slit S of the collimator. The radiations after passing INFLUENCE OF ELECTRICAL FIELDS 3 through the echelon prism E were analyzed by a flint glass prism F,of 6o° angle, so that in the focal plane of T there appeared whatlooked like the ordinary line-spectrum of the source, except that someof the lines might be double and might have
The Astrophysical journal . rtical axis so that a considerable part ofthe spectrum could be brought into focus at one time. The mounting of the instrument was arranged as in the diagram(Fig. 1). Usually the source of light studied was placed directly infront of the slit S of the collimator. The radiations after passing INFLUENCE OF ELECTRICAL FIELDS 3 through the echelon prism E were analyzed by a flint glass prism F,of 6o° angle, so that in the focal plane of T there appeared whatlooked like the ordinary line-spectrum of the source, except that someof the lines might be double and might have a few satellites. Theseapparently double lines of course were different orders of the sameline, their angular distance apart being \/e, where e was the widthof the step. The linear distance between the orders on the photo-graphic plate was approximately mm. Except for quite complexsources, there was no difficulty in identifying the lines. This simplemethod of separating the lines is greatly to be preferred to that of K. Fig. 1 analyzing the light before it enters the collimator, for in the lattermethod the lines of the spectrum have to be examined or photographedseparately. In this method they all can be photographed at strips of the echelon (1 mm in width), the slit of the collimatorand the edge of the prism were made vertical. In front of the slit of the collimator was a movable diaphragm bymeans of which the upper or lower half of the slit could be exposedto the source. For example, if the Doppler effect in the canal raysof mercury was to be tested, one-half of the slit was exposed to thecanal stream directed at about io° to the axis of the collimator, thenthe other half of the slit was exposed to an ordinary mercury-spectrumtube. Fig. 2 shows the appearance of a plate (enlarged two diam-eters ; the fine lines have been lost in the process) when canal rays inhelium (a) and a helium-spectrum tube (b) were sources. If any Dop-pler effect was present, it would be
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectspectru, bookyear1895
