1835.] the Advancement of Science. 217 



calculation. The discussion was discontinued, in conse- 

 quence of the press of business. 



Professor Rigaud made some observations. 



23. Colonel Sykes read various details as to the mode of 

 conducting observations on temperatures, as practised by 

 himself in India, with a general statement of his results. 

 His method was to determine the boiling point of water, 

 at the altitude he wished to fix. In several examples the 

 error was only 1 6 feet in 4000. The apparatus recommended 

 was very simple, cheap, and portable. 



24. Mr. M'Cullagh, on reflection and refraction of polarized 

 light at the surfaces of crystals. This communication con- 

 sisted of the results of a mathematical investigation of cer- 

 tain questions relative to the polarization of light, which 

 arise on comparing the theories of Fresnel and Cauchy, and 

 was full of most important views. 



25. Mr. M'Gauley, on Magnetism. This paper was a con- 

 tinuation of his former communication, in which the author 

 entered at large into his theory of electro-magnetism, con- 

 tending that it is merely a state of electric excitation, reject- 

 ing the theory of currents, and concluding with observations 

 in favour of free inquiry on philosophical subjects. 



Friday, 14M August. — 26. Professor Apjohn, on the Dew 

 Point. The author propounded a formula of connexion 

 between the dew point and the indication of the wet bulb 

 thermometer. His results tended to shew the conformity 

 of observations and theory. 



27. Professor Hamilton read an abstract of Mr. Challis's 

 results respecting the simultaneous vibrations of a cylindri- 

 cal tube, and the column of air contained in it. 



In the theory of cylindrical tubes, it is necessary to take 

 into account the vibration of the tube itself, as well as the 

 air contained. Certain laws have been deduced. It is pro- 

 bable that the vibrations of the pipes severally affect the 

 vibrations of the columns of air, and, consequently, the 

 sound produced. 



28. Professor Wheatstone, on Speaking Machines. The 

 author noticed the attempts made by the Germans to form 

 pipes which would imitate the vowel sounds, De Kemplin 

 imitated different sounds with a conical tube, more or less 

 covered at the mouth. The author observed that the differ- 



