232 Analyses of Books. [Sept. 



the different substances examined in contact with milk, and 

 observe whether they coagulated that liquid. The results were 

 as follows : — 



The mucus of the fourth cavity of a calf's stomach coagulated 

 milk, but not the mucus of the first, second, and third cavity. 

 After a calf has left off sucking, the inner member of the fourth 

 cavity of the stomach still coagulates milk. Only that part of a 

 hog's stomach near the pylorus, where the gastric glands are 

 situated, coagulates milk. The crop and gizzard of a cock 

 coagulated milk, the latter more speedily than the former. The 

 contents of a shark's stomach, and the stomach itself, coagu- 

 lated milk immediately. Rennet from the stomach of the sal- 

 mon and thornback coagulated milk. From other experiments, 

 Sir Everard Home concluded, that the secretion of the gastric 

 glands possesses the power of coagulating milk, and that it 

 gives that power to all the parts by which it is imbibed, whe- 

 ther composed of living parts or not. 



XIII. On some Properties of Light. By David Brewster, 

 LL.D. F.R.S. Edin.] These properties are divided into four 

 sets : I. On a new Property of Refracted Light. Thin plates 

 of agate, calcedony, and carnelian, gave a distant image of any 

 luminous object; but on each side of this image was one highly 

 coloured, forming with it an angle of several degrees, and so 

 deeply affected with colour that no prism of agate, with the 

 largest refracting angle, could produce an equivalent dispersion. 

 The light which constituted all these images was polarized. The 

 effect of two plates of agate is similar to what was observed by 

 Biot. There is a faint nebulous light, unconnected with the 

 image, but always accompanying it. This Dr. Brewster con- 

 jectures may be owing to an imperfect double refractive power 

 in the agate. 2. On the double refractive Power of Chromale of 

 Lead. The refractive power of this substance is thrice as great 

 as that of Iceland spar. 3. On Sid>stances with a higher reji ac- 

 tive Power than the Diamond. The following is the refractive 

 and dispersive power of different substances, according to Dr. 

 Brewster : — 



Refractive Powers. 



Chromate of lead, greatest refraction . .2*926 



Ditto, least refraction 2*479 



Realgar .2*5 1 



Diamond, according to Newton 2*439 



Phosphorus 2*224 



Sulphur, native 2*1 15 



Cryolite 1*344 



Ice 1*307 



