344 Proceedings of the British Association. 



tegral amount of wind shown by it at Plymouth for the entire 

 year, and in the mean time he sent drawings and tables which 

 contain the results of its work for the last three months. 



Sir David Brewster then offered some remarks on microscopes, 

 and his mode of illuminating microscopic objects. 



Prof. Nichol gave an account of the astronomical observatory 

 erecting near Glasgow. Two reflectors by Ramage had been ob- 

 tained, one of 25 feet focal length, to which Sir J. Herschers 

 collimator is to be affixed, and another of 55 feet focal length and 

 23 inches in diameter. A transit-circle had been been ordered 

 from Munich, the telescope of which is 8 feet focal length and 

 6.25 inches diameter. An equatorial of great power was also in 

 expectation. 



Mr. Airy, the astronomer royal, gave an explanation of a new 

 apparent polarity of light, announced some time since by Sir D. 

 Brewster. His explanation resulted in showing that the phenom- 

 enon is a simple consequence of the undulatory theory. Sir D. 

 Brewster remarked that Prof Powell's solution of this problem 

 was fallacious, and that of Mr. Airy did not explain all the facts. 

 A full account of experiments on the phenomenon in question is 

 now preparing for the Royal Society. 



Sir D. Brewster gave an account of a rainbow seen in Dumfries- 

 shire by Rev. Mr. Fisher, in which the primary bow was accom- 

 panied with jive supplementary bows, and the secondary one with 

 three; a larger number than had been before noticed. 



Mr. Airy explained the principles of Mr. Fowler's new calcula- 

 ting machine, the object of which was to facilitate the guardians 

 of a. poor-law district in Devonshire, in calculating the proportions 

 in which the several divisions were to be assessed. 



Dr. Anderson then submitted some observations on the dew 

 point, in which he explained the principles of the formula which 

 he deduced several years ago, from the experiments of Dalton and 

 Gay-Lussac, for determining the various objects connected with 

 the hygrometric state of the air : and showed by means of tables 

 which he had constructed from it, the facility and dispatch with 

 which the absolute as well as the relative humidity of the atmos- 

 phere, together with the dew point, might be obtained. 



Mr. Shand read a paper on the agency of sound, adverting to 

 the rules and principles by which it is governed, and with partic- 

 ular reference to the economy of voice in public apartments. 



