Mr Stewart's Meteorological Observations, SfC. 105 



of my paper in 1815, and also by observations of MM. Arago 

 and Biot ; and it has been adopted by Fresnel as a law rigor- 

 ously physical, and enters into the beautiful formulae with which 

 he has enriched the science of optics. It derived also additional 

 support from the numerous observations made by M. Arago 

 and myself, on the change in the plane of polarization produ- 

 ced by reflexion. 



The results of Dr Seebeck respecting the cause of the super- 

 ficial changes in glass and other bodies, are, as he allows, not 

 perfectly satisfactory. I had shown in my first paper, {Phil. 

 Trans. 1815, p. 124, 125,) that the anomalies in glass arose 

 from a chemical change in the surface, which was sometimes 

 obvious even to the eye, and from oxidations produced by the 

 action of the air, and by heat. In a subsequent paper on a 

 different class of phenomena, (See Phil. Trans. 1829, and 

 this Journal, No- ii. N. Series, p. 209, &c.) I have shown how 

 to detect these oxidations when they are wholly invisible to 

 the eye ; and I have proved that they take place on some kinds 

 of glass, and not. on others. It would be desirable, therefore, 

 that Dr Seebeck should repeat his experiments with the glass 

 E, and examine the state of its surface when it gives different 

 angles of polarization, by examining the pencil reflected from 

 these surfaces, when they are covered by an oil of the same 

 refractive and dispersive power. A slight absorption of some 

 of the minutely divided matter, used in grinding and polish- 

 ing the surface, may account for the anomalies in question in 

 those cases, if any really exist, where they are not produced 

 by oxidation. 



Art. XII. — Abstract of Meteorological Observations made 

 in the Isle of Man from 1822 to 1831. By Robkiit Stew- 

 A KX, Esq. Receiver-General of the Isle of Man. Commu- 

 nicated by Dr IIlBBERT. 



In Number X. of this Journal, p. 2.S1, we have already given 

 an abstract of Mr Stewart's valuable observations made from 

 1822 till 1820'. The thermometer was situated in a northern 

 exposure, and was observed at o'clock a. m. and 11 o'clock 

 P. m. The following are the observations made since 1825. 



