PASSAGES FROM POPULAR LECTURES. 
48 
* Hordeum pratense. Scattered variously, luxuriant. Beckford near 
Evesham. 
Lolium perenne. Grass fields. 
* Nardus stricta. Commons. 
* Asplenium Trichomanes. Cookley. 
Scolopendrium (vulgare). Rocks near Bell’s Mill; Chaddesley; 
Hill Pool; very rare. 
+ Lycopodium clavatum. Whittington Common ( Stafford ); very 
rare. 
Scott deserves our gratitude notwithstanding the imper¬ 
fection of his work, as his Catalogue yields many new county 
records. 
(To be continued.) 
PASSAGES FROM POPULAR LECTURES. 
BY F. T. MOTT, F.R.G.S. 
III.—BINOCULAR VISION. 
FROM A LECTURE ON “ARTIFICIAL EYES,” 1867. 
[Note.— Numbers I. and II. of these “Passages” will be found in 
the “ Midland Naturalist, Vol. I., page 29, and Vol. II., page 29. 
The series was cut short by other engagements. I propose 
now to continue it.—F. T. M.] 
Having two eyes, why do we not see everything double ? 
The first answer is that we do see many things double ; more, 
probably, than most of us are conscious of. There are certain 
conditions under which we see things double, and certain 
others under which we see them as one only. Probably 
infants in their earliest months see everything double. If 
you hold up your finger between your face and some other 
object not very far off, and then look at the finger you will see 
two images of the other object, and vice versa. If you are 
foolish enough to drink beer or brandy to excess, so as to 
over-stimulate and confuse the brain, you will most likely 
experience double vision, accompanied by other curious and 
undesirable symptoms. 
Single vision with two eyes, like the hearing of one sound 
with two ears, seems to depend upon a combining power 
which the healthy brain possesses, partly due to the fact that 
the optic nerves are actually united within the brain, and 
partly to experience acquired in very early life. But one 
necessary condition is that the eyes should be both directed 
