102 British Association for the Advancement of Science. 



laminas, were reflected at the hinder surface, and came out again 

 after refraction at the first. Now it is obvious that the necessary 

 conditions of acceleration and retardation of the rays could be 

 thus obtained ; and the vast multitude of exceedingly thin laminae 

 which are produced in the plate of mica, by the process of Prof, 

 Forbes, far surpassed any thing which, by the most delicate me- 

 chanical operations we can hope to obtain. These researches are 

 also of the utmost importance as tending to throw light on the 

 internal structure of metals. Young, with his usual sagacity long 

 since conjectured, from the well known fact that very thin leaves 

 of gold transmit greenish hght with almost unimpaired regularity, 

 that the surfaces of all metallic plates consist of very thin lam- 

 inae, pervious to light, and that the phenomena of their polari- 

 zing influences depended on this. Fresnel followed out this con- 

 ception, and traced mathematically the mode in which the polar- 

 ization would take place. The present researches not only con- 

 firm these views, which were heretofore only conjectural, but 

 actually show, how under certain conditions, elliptic and circular 

 polarization could be obtained by a method similar to that produ- 

 cing ordinary polarization. 



Mr. J. F. Goddard described an apparatus which he had con- 

 structed, by means of which he could exhibit in the Oxyhydrogen 

 microscope, all the beautiful phenomena of polarized light. 



Mr. Addison presented tables of meteorological observations 

 made at Great Malvern, in Worcestershire, from 1835 to 1838 

 inclusive. From these tables it appears, that the mean tempera- 

 ture of Malvern is 47.7° ; the mean barometrical pressure is 

 29.386 in., and the mean dew point at 9 A. M., is 43.7°. The 

 range of temperature during the four years, is from 9° on the 

 20th of January, 1838, to 84° on the 5th of July, 1836. The 

 range of the barometer is from 28.010 in., November 29, 1838, to 

 30.228, October 14, 1837. 



Mr. Julius Jeffreys offered a few observations on the m,eteorol- 

 ogy of elevated regions. In 1824 he traversed through a space 

 of 200 miles the higher range of mountains in the protected 

 States in the Himalayas, for the purpose of conducting inquiries 

 into the meteorology of those regions, and the character of the 

 climate in a medical point of view. His observations were made 

 during six months, upon mountain heights and in their subjacent 

 valleys; from an elevation of 16,300 feet down to 4,000 ; and of 



