appears with a silver white space round it: then follow, in decreasing distances, various insulated rings, all consisting of three colours, which are in immediate contact with each other. Each of these rings, of which perhaps three or four might be counted, is yellow on the inner side, blue on the outer, and red in the centre. Between two rings there appears a silver white interval. The rings which are farthest from the centre are always nearer together: they are composed of red and green without a perceptible white space between them.
434.
We will now observe the appearances in their gradual formation, beginning from the slightest pressure.
435.
On the slightest pressure the centre itself appears of a green colour. Then follow as far as the concentric circles