394 Proceedings of the British Association 
up :—We have on the one side four new forces assumed,—the optic at- 
tractive force and the optic repulsive force, the magno- -crysiallic force and 
-the magneto-crystallic force ; and on the other side no new force what- 
ever, but simply that modification of exislitg forces which we have named 
. ero any By at tention to the compression of amor Weitis ye 
ape: 
oe A 
ia! per gave rise to a very animated discussion.—The Presiden 
= id, pave Ree he was ready to admit that Mr. Tyndall’s rob was 
; & _ most ingenions,, and the arguments and experiments by whic 
* tained. his views.were apparently well conceived and sound, yet time 
» ‘must be given to weigh them, well before, a -satisfactory conclusion 
could be reached.—Prof. _Themson thought that Mr. Tyndall’s views 
would be found -jo:be omens consonant with Dr. Faraday’s and the 
ae theory of Poissgn. ‘ 
On the Polarizing Sirueture of the Eye; by Sir D. Brewster. 
The author said that when he sat down to in paper he was 
Prof. S a 
the polarizing structure of the eye for the p 
ereshee, which would be referred to them, immediately by. Mr. Stokes. 
He would, therefore, confine himself to showing, that the eye contained 
within itself amply sufficient to account for the. phenomenon, because 
constituting the eye itself an ever ready pelerecope <i analyzer of po- 
d 
tion, viz., that it ought to turn round the brush 45° from the ane of 
‘ization. a which plane, on the Resse the brush was found to 
arrange itse 
On Haidinger’s Brushes ; by Prof. G. G. Sroxes. 
It is now several years since ifibee brushes were discovered, and they 
have yee been observed by various Fs omga sed but the author has 
with. any observations made with a view of investigating the 
action of different colors in prodiciag the brushes. The author’s at- 
tention was first called to the subject by observing that a green tourma- 
line which polarized light very imperfectly enabled him to see the 
he 
tourmaline which transmitted a much smaller quantity of unpolari 
light. e then tried the effect of combining various colored glasses 
