Dr, Reuben on moving Blood-corpuscles within the Retina. 333 
applicable to these; and being set aside as but an incidental, pos- 
ibly a modifying circumstance, no probable hypothesis other 
than that of action of the corpuscles as lenses seems to remain. 
nother curious phenomenon I early observed, and one 
for which I have not been able even to imagine a cause. It ap- 
pears with most of the media used, especially with the darker 
colors; and usually precedes or attends the vision of the shining 
traces, i 
gitation, or swarming, as it might be termed, 
over the whole field of view. These appear‘to be more distant 
than the lucid points, and equally diffused; and they are seen 
and the appearance suggests 
_ Streams covered with fine floating ice. But the eye must be 
1s uniform and their numbers greater. 
IIT. The following notes I select from among such as I have 
taken down during some of my latest experiments, the past 
autumn : 
a.—With a bright sun; view of thesky about 20° from the sun, 
through the cobalt glass: When the lucid lines are best seen, and 
