452 Proceedings of Philosophical Societies. [Dec. 



flesh. The object of the author was to show that granulations 

 which appear to consist of a congeries of tortuous vessels, are 

 formed in a manner very similar to the blood vessels, &c. 

 described by him in a former paper* Pus, according to Sir E., 

 when first secreted, is a transparent fluid. A pellicle of pus in 

 this state covers the little prominences of the granulations. Under 

 this pellicle particles of air are exuded, upon which vessels appear 

 to be moulded. These vessels soon become distended with red 

 blood. They anastomose freely, and chiefly lie horizontally, though 

 minute red spots are also apparent, which seem to be the termi- 

 nations of vessels running in a perpendicular direction. The air 

 exuded, and upon which the vessels are formed, Sir E. consi- 

 ders, as in former instances, to be carbonic acid gas. 



Drawings, illustrative of these and the subsequent changes, 

 made chiefly from the observations of Mr. Bauer, accompanied 

 the paper. 



Nov. 12. — A paper, by Dr. Brewster, " On the Laws which 

 regulate the Absorption of Polarised Light by Doubly Refracting 

 Crystals," was read. The author was led to investigate these 

 laws, by observing the phenomena presented by the acetate of 

 copper when exposed to polarised light. The first section of his 

 paper treated of the absorption of polarised light by crystals of 

 one axis, and contained the details of a great number of observa- 

 tions. Crystals having more than one axis were afterwards sub- 

 mitted to similar experiments ; and the paper concluded with 

 remarks upon the effects of heat in modifying the absorption 

 of polarised light by crystallized bodies. Under this head was 

 related a curious fact, which may be of use to lapidaries. Heat 

 does not, as is commonly supposed, produce the pink colour of 

 some topazes, but merely discharges the yellowish colouring 

 matter of one medium, and leaves the pink colouring matter 

 which originally existed in the other. If, therefore, a pink colour 

 exists in one of the images of a topaz seen by polarised light, 

 the topaz will become pink on the application of heat. 



It is not easy to give a complete abstract of a paper by simply 

 hearing it read, especially when,, like the present, it contains a 

 great number of minute details. Dr. B., however, appeared to 

 conclude from his experiments, that the colouring particles of 

 crystals are not dispersed indiscriminately throughout their mass, 

 as usually imagined ; but are confined to different media, or 

 rather that they possess an arrangement connected with the 

 ordinary and extraordinary forces which they exert upon light. 



Nov. 19 — The Society met, but no paper was read, on account 

 of the death of the Queen. 



* See Annait of Philosophy, xi. 63, 298 : also the preceding page. 



