1824.] Proceedings of Philosophical Societies. 305 



XXXI. On certain Changes which appear to have taken place 

 in the Position of some of' the principal Fixed Stars. By John 

 Pond, Esq. Astronomer Royal, FRS. 



This communication chiefly consists of a series of tables of 

 observations on the stars ; confirming, in Mr. Pond's judgment, 

 his doctrine of their southern motion. — B. 



Article XVI. 



Proceedings of Philosophical Societies. 



ROYAL SOCIETY. 



Feb. 19. — A Series of Meteorological and Astronomical 

 Observations made in New South Wales, and on the Voyage to 

 that Country, were presented from Major-Gen. Sir T. Brisbane, 

 KCB. FRS. 



A paper was read, " On the Semi-decussation of the Optic 

 Nerves ; by W. H. Wollaston, MD. VPRS." 



It has been generally concluded by anatomists, and they sup- 

 port the conclusion from the observation of the arrangement of 

 the optic nerves as distinctly seen in certain kinds of fishes, that 

 in the human eye, the optic nerves, after passing from the 

 thalami nervorum opticorum, meet, and then proceed appa- 

 rently in union, though in reality still separate ; so that the 

 right eye is believed to be entirely supplied with these nerves 

 from the left thalamus, and the left eye from the right thalamus : 

 and this arrangement is called the decussation of the optic nerves. 

 The consideration of a particular species of blindness, however, 

 has led Dr. Wollaston to a somewhat different distribution of the 

 optic nerves. After fatigue, arising from four or five hours' 

 violent exercise, Dr. Wollaston was affected by a partial blind- 

 ness, of which he first became sensible by seeing only half the 

 face of a person near him, and next by seeing only the termina- 

 tion " son " of the name " Johnson ; " this blindness was to the 

 left of the point of vision in each eye ; it was not perfect dark- 

 ness, but merely a dark shade ; and in about fifteen minutes, it 

 gradually passed off, in an oblique direction upwards towards the 

 left. As it was referable to an affection of the nerves, Dr. W. 

 did not apprehend or experience any return of it, other nervous 

 affections being produced by fatigue. Some years afterwards 

 he again experienced this singular kind of blindness, without 

 any obvious cause, and first became sensible of it likewise by 

 seeing only the half of a person's face ; but in this case the right 

 side of both eyes was affected, and complete vision was suddenly 

 restored by the joy produced on receiving information of the safe 

 arrival of a friend from a hazardous enterprise. Dr. Wollaston 

 has a friend who has experienced the same affection for 6even- 



New Series, vol. vn. x 



