PRACTICAL EXERCISES 



glass, in your own eye, the 



contract. hen the eye is accommodated tor a ^^ at 



(c) Observe that when _ x ? when a distant oop ^ Qn 



st - to - 



of the rotating discs, ^y ^^ paper ^stened. o ^ 



produced, and any ^. hed b y adding white to J^e three 



thirty s econd f th a e fi lame nt will appear dark^ or forty 



r: 



" 



' - 



