&66 Dr. HERScftEi/s Investigation of the Powers, 



G. Full as bright ; and as many points visible. Very distinct. 



B. Much less bright. Very distinct. 



I. Still less bright. Very distinct. 



V. Much less bright again. Very distinct. 



6th Experiment. I viewed a guinea, at 9 feet 6 inches from 

 the prism ; and adjusted the place of the object in the several 

 rays, by the shadow of the guinea. If this be not done, decep- 

 tions will take place. 



R. Four remarkable points. Very distinct. 



0. Better illuminated. Very distinct. 



Y. Still better illuminated. Very distinct. The points all 

 over the field of view are coloured ; some green ; some red ; 

 some yellow; and some white, encircled with black about them. 



Between yellow and green is the maximum of illumination. 

 Extremely distinct. 



G. As well illuminated as the yellow. Very distinct. 



B. Much inferior in illumination. Very distinct. 



1. Badly illuminated. Distinct. 



V. Very badly illuminated. I can hardly see the object at all. 



yth Experiment. The nail again, at 8 feet from the prism. 



R. I attended to two bright points, with faint ones between 

 them. Almost all the points in the field of view are red. Very 

 distinct. 



O. I see all the points better : they are red, green, yellow, 

 and whitish, with black about them. Very distinct. 



Y. I see better. More bright points, and more faint ones: 

 the points are of various colours. Very distinct. 



G. I see as well. The points are mostly green, and brightish- 

 green, inclining to white. Very distinct. 



B. Much worse illuminated. Very distinct. 



