time, some experiments for determining the actual effect on the vi- 

 brations of the pendulum, by changes of temperature, independently 

 of any theoretical allowance. 



The portion of Captain Hall's letter, which was not adapted to 

 public reading, consists of six series of observations at London, the 

 Galapagos, San Bias, and Rio de Janeiro. These are given in the 

 fullest detail, together with every attendant circumstance likely to 

 have any effect on the experiments. 



Second Part of the Paper on the Nerves of the Orbit. By Charles 

 Bell, Esq. Communicated by Sir Humphry Davy, Bart. P.R.S. 

 Read June 19, 1823. {Phil. Trans. 1823, p. 289.] 



This is a paper in continuation. In this part the author states 

 that there are six nerves of the brain which go to the , eye, while 

 there are in all only nine nerves coming from the brain. He pro- 

 ceeds to show that each nerve has a distinct or appropriate function. 



The branch of the fifth nerve, called Ophthalmicus, bestows upon 

 the parts within the orbit and the coats and surfaces of the eye, sen- 

 sibility to pain, and that modification of sensibility which causes the 

 winking and rapid motions of the eyelids and eyeball, and pro- 

 duces tears. It is shown that by the loss of this nerve the eye is 

 deprived of its sensibility to touch and irritation, while it continues 

 to enjoy the sense of vision, and the motions of the eye and eyelids 

 remain perfect. 



Having shown that the motions of the eyelids depend on a 

 branch of the seventh nerve, and not on the fifth, as hitherto sup- 

 posed, and having proved in the former part of the paper that there 

 is a corresponding motion of the eyeball and eyelids, necessary for 

 the preservation of the organ, he proceeds to show that this connex- 

 ion is established through the fourth nerve ; that the fourth, or troch- 

 learis, goes to that muscle which performs the instinctive and insen- 

 sible motions of the eyeball, in sympathy with those of the muscles 

 of respiration, and consequently with the eyelids. 



Having thus shown that the fourth, and a branch of the seventh, 

 as enumerated by authors, perform the instinctive and involuntary 

 motions of the eyeball and eyelids, he then explains the office of 

 the third and sixth to be exclusively for the voluntary motions of the 

 eye, and for directing the eyeball in subservience to its office of 

 vision. 



By the discovery of the peculiar functions of the fourth, fifth, and 

 seventh, the nerves, of the head become thus arranged according to 

 their uses : 



The first is the olfactory nerve. 



The second is the nerve of vision. 



The third is for the voluntary motions of the eye. 



The fourth for the instinctive motions of the eye. 



The fifth entirely for sensation of the head generally, and for the 

 regulation of certain motions of the jaws. 



o 2 



