392 



Report of the Committee on Colour- Vision. 



Appendix IV. 



Dr. Jeaffreson's Test Disc. 



Dr. Jeaffreson's test apparatus consists of a rotating celluloid 

 disc, about a foot in diameter, upon which skeins of wools are 

 arranged radially at the outer edge (see Fig. I). All of the 



Fig. I. 



iisc except a small aperture, as shown in Fig II, is covered. 

 By means of a button attached to its centre, the disc can be 

 turned until any colour is brought opposite to that standard test 

 colour which is seen in the upper aperture. The test skeins 

 are the three Holmgren test colours, and a yellow, blue, and 

 purple. The apparatus is mounted in a frame, so that it can be 

 hung upon the wall. 



In using the test the usual course is to point out to the person 

 under examination the pale green wool in the upper aperture, and 



