next, or perhaps modified in a parallactic sense by the oppositely acting one, the whole mass being thus changed to a thread-like appearance.
427.
Lastly, it is to be remarked that if we look through the blades towards a minute light in the window-shutter, coloured stripes and halos appear on the retina as on the paper.
428.
The present chapter may be here terminated, the less reluctantly, as a friend has undertaken to investigate this subject by further experiments. In our recapitulation, in the description of the plates and apparatus, we hope hereafter to give an account of his observations.41
XXXIII.
EPOPTICAL COLOURS.
429.
We have hitherto had to do with colours which appear with vivacity, but which immediately vanish again when certain conditions cease. We have now to