PHYSIOLOGICAL ACTION OF LIGHT. 147 
SERIES IT.—Rassir’s Eye.—Source of light, a magnesium lamp. Neutral point, + 195; 
polarity, + 175; total first deflection, 150. 
Obs. 11. Before the impact of light the reading on the galvanometer scale 
was at 225, giving a total deflection of 150. On the impact of light it fell at 
once to 215—a fall of 10. The electro-motive force now diminished in the dark 
as follows, at intervals of 15 seconds :—Obs. 12 to 27—190, 185, 180, 175, 170, 
165, 162, 160, 161,159, 157, 156 155, 153, 152, 150, 149. 
_ Obs. 29. A heated poker brought near it caused an immediate rise to 190. 
On the removal of the poker, it fell slowly to 153. The following four experi- 
ments were then made, the source of light being the flame of a magnesium 
lamp held at a distance of three feet, and allowed to fall directly on the eye :— 


| . 
Readings of 
Galvanometer scale | Effects of the Effects of the 
Obser- before impact, impact of removal of Remarks. 
vations. at intervals of light. light. 
15 seconds. 


30 153, 153, 152, | 143, or fall of 7 | 146, or rise of 3 
he Wa Ths) 
iat ae a The result of these four 
Pe iG iG | 132) or ful of 51140, or rice of 9, “<Pomments i= 2 fall of 
bout 5 degrees on the 
145, 144 ee g) 
oe 143. ; impact of light, and a 
eG 108140), 135 or filos 5 , 137, orice of 2| . "°° : bagiees Glas 
140, 140, 140 sea 
33 | 135, 135, 135, | 128, or fall of 5 | 130, or rise of 2 
133, 133),133 






After readjusting the eye on the cushions, the following experiments were 
made, in which the light was passed through a flat-sided glass vessel filled with 
water, one inch in thickness. The source of light, as before, was a magnesium 
lamp :— 




Obser- Before After After Effect of Effect of 
vations. impact. impact. removal. impact. removal. Remarks. 
34 110 105 106 Fall of 5 | Rise of 1 
35 104 103 105 Fall of 1 | Rise of 2 | Result is a fall of about 
36 100 97 98 Fall of 3 | Rise of 1 3 degrees on impact 
37 94 91 92 Fall of 3 | Rise of 1 of light, and a rise 
38 90 87 89 Fall of 3 | Rise of 2 of 2 on removal of 
39 86 83 85 Fall of 3 | Rise of 2 light. 
40 81 78 80 Fall of 3 Rise of 2 




