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THE POLARISCOPE AS APPLIED TO SUGAR ANALYSIS.to sacrifice the delicacy of the reading in order to obtain the passage of morelight, the accuracy of the observation being thereby increased. An instrumentusing the Landholt lippich half shadow device, and in which the half shadowangle can be varied at will, has been devised by Bates, and constructed by thefirm of J. and J. Fric. The analysing nicol and the polarizing nicol aremounted in bearings, and are joined by gears with a connecting rod ; the gearsare controlled by the rotation of a milled head, and are such that the rotationof the analyser is always twice that of the polarizer. A scale attached to themilled head gives the half shadow angle.FIG. 239.The zero of the instrument is affected by a change in the half shadowangle; with an instrument adjusted for a half shadow angle of 10°, the lattermay be varied from 4° to 12.4° with the introduction of an error of less than.1 Ventzke. Bates has worked out the corrections to be made for differenthalf shadow angles when the instrument is in adjustment for the latter equalto zero, and this can be made practically instantaneously, the half shadowangle being indicated as already mentioned.437