838 Proceedings of Royal Society of Edinburgh. [sess. 
Expt. 3. Comparison of action of light and of radium on same eye. Eye 
adjusted on clay pads, so that it could be submitted to action either of 
radium or to the light from a taper held 2 feet from eye. 
Resting current, 40 divs. Radium on, rise of 1 div. ; very slight fall ; 
very slight rise ; radium off, rise of 1 div., then fall to nearly 40. Radium 
removed from box. Eye in dark for five minutes. Light on, rise of 10 divs., 
slight fall ; rise of 1 div. ; light off, rise of 5 divs., then fall to somewhat 
below starting point. Rest for three minutes. Light on, rise of 6 divs. ; slight 
fall ; light off, rise of 2, then fall. The eye was then readjusted on the pads.. 
Total resting current, 70 divs. Light on, rise of 8 ; slight fall ; light off, 
rise of 5 divs., then fall. The radium was again introduced and was placed 
nearer the eyeball. Total resting current, 70 divs. ; radium on, rise of 7 divs. ; 
radium off, rise of 5, then fall. 
Two other experiments may be quoted, the one showing action 
of light and the other the action of radium. 
Light. Fresh Eye. A. 
(1) Resting current, 22 divs. ; light on (taper, 2 feet off), rise to 26 divs.,. 
steady for one minute ; light off, rise to 30 ; fall to 21 divs. 
(2) Resting current, 19 divs. ; light on, rise to 26, fall to 20, rise to 27 
divs. ; steady ; light off, rise to 30, fall to 21 divs. 
(3) Resting current, 19 divs. ; light from red lamp, 2 feet off, rise to 20, 
fall to 18 '5 divs. ; light off, rise to 21, fall to 18 ’5 divs. 
(4) Resting current, 13 divs. Red light on, rise to 19, fall to 18, rise to 
19, fall to 17 divs. ; light off, rise to 21, fall to 16 divs. 
It is interesting to note that in this experiment the eye was- 
sensitive to the rays of red light from a lamp which we employ in a 
photographic chamber. 
Radium. Fresh Eye. B. 
(1) Large resting current; T V = 20 divs. ; radium on, rise of ’5 div., 
slight fall ; radium off, rise of *5 div., then fall. 
(2) Full current used, without shunt = 120 divs. Radium on, rise of 
3 '5 divs., slight fall ; radium off, rise of 3 divs., then fall. 
(3) Repeated, radium on, rise of 2 divs., fall of 15, rise of 1*5, fall of 1 
div. ; after two minutes’ exposure, radium off, rise of 3 divs., then fall to 
original position. 
(4) Full current, 54 divs. ; radium on, rise of 2 ‘5, fall of ’5, rise of l - 5 
div. ; radium off, rise of 3 divs., fall to 53 divs. The radium was removed 
and eye kept in dark. We note also that ten minutes thereafter the resting 
current was 44 divs. ; light on, rise of 11 div. ; steady ; light off, rise of 6 
divs. , and then fall to 43 divs. 
Repeated experiments similar to Expt. (3 B) gave similar results. 
With radium on there was always a rise of 2 to 3 divs., then 
a slight fall, say of 1-5, then a second rise of 1 div., and then a 
slight fall. With radium off there was a slight rise of usually 
1 div., and then a rapid fall off towards original position. After 
