1815.] , Royal Society. 69 



Rev. Charles Burney, LL. D. 



Charles William, Earl of Charlevillc. 



Davies Giddy, Esq. M. P. 



Sir Everard Heme, Bart. 



James Horsburgh, Esq. 



Alexander Marcet, M. D. 



Thomas, E?rl of Selkirk. 



Henry Warburton, Esq. 

 The number of deaths since the last anniversary election has 

 been 16; the number of new members admitted, 23. The num- 

 ber of ordinar . members on the election list amounts to 580, that 

 of ioTe\s;a members to 43, making a total of 623 members. 



On Thursday Dec. 8, Dr. Brewster's paper on the depolarisation 

 of light by different bodies was continued. He gave a long list of 

 animal, vegetable, and mineral bodies, that have the property of 

 depolarising light; together with a list of bodies that have no 

 eflFect in producing this depolarisation. He then gave his theory of 

 this depolarisation. Bodies capable of depolarising light may be 

 divided into seven classes. 1 . Those that have a neutral axis and 

 produce a double image. With respect to these bodies the theory 

 is evident. 2. Those that have a neutral axis but produce only a 

 single image, as the human hair. In these bodies he supposes that 

 two images are really produced, but that they coincide with each 



other. 



On Thursday Dec. 15, Dr. Brewster's paper was concluded. 

 He continued his enumeration of the dilFereut classes of depola- 

 rising bodies as follows : 



3. Those that have no depolarising axis but depolarise light i^ 

 every dhection, as gum arable. These he conceives to be com- 

 posed of layers placed one over the other, each of which has a de- 

 polarising axis ; and as these axes are placed in every direction, 

 the body acquires the property of depolarising in every direction. 

 4. Those bodies that have an approximation to a neutral axis, as 

 gold-beater's skin. 5. Those that have an approximation to a 

 depolarising axis. G. Those that allow the light nearly to vanish, 

 but not quite, at every alternate sector, as oil of mace. 7- Those 

 that allow it to vanish entirely at every alternate sector, as calca- 

 reous spar, when the light passes through the shorter axis. 



At the same meeting part of a paper by Benjamin Travers, Esq. 

 was read. On the Mechanism by wliich the Eye adjusts itself to dif- 

 ferent Distances. The paper was drawn up with uncommon clear- 

 ness, and even elegance. It consisted of three parts: 1. A sketch 

 of the difierent liypotheses to which this mechanism has been 

 ascribed, with the author's reasons for not admitting them. These 

 arc the muscles of the eye, the ciliary processes, the supposed 

 muscularity of the lens itself. 2. An account of the anatomy of 

 the eye, as far as it is requisite for the purposes of the paper. 

 3. His reasons for believing that external pressure is applied lo the 

 lens, and that this pressure is suflicient to alter its shape. 



