X. Ona definite arrangement, and order of the appearance and progress, of the 



Aurora Borealis ; and on its height above the surface of the earth. In a 

 letter to Davies Gilbert, Esq. M.P. President of the Royal Society. 

 By the Rev. James Farquhakson, Minister of the Parish of Alford, 

 Aberdeenshire P^^g^ 103 



XI. Observations on the functions of the Intestinal canal and Liver of the human 



Fcetus. By Robert Lee, M.D., Physician to the British Lying-in^Hos- 

 pital. Communicated by Dr. Prout, F.R.S. 121 



XII. Ea-periments on the modulus of Torsion. By Benjamin Bevan, Esq. 



Communicated by the President 127 



XIII. On a Differential Barometer. By the late William Hyde Wollaston, 

 M.D. F.R.S. Communicated by Henry Warburton, Esq. F.R.S. . 133 



XIV. Some observations relating to the function of digestion. By A. P. W. Philip, 



M.D. F.R.S. L.SgE. 137 



XV. Experiments on the friction and abrasion of the surfaces of solids. By 



George Rennie, Esq. F.R.S. 143 



XVI. An attempt to rectify the inaccuracy of some logarithmic formulae. By 

 John Thomas Graves, of the Inner Temple, Esq. Communicated by 

 John Frederick William Herschel, ^lyg-. ^. P 171 



XVII. On the reflexion and decomposition of light at the separating surfaces of 

 media of the same and of different refractive powers. By David Brew- 

 ster, LL.D. F.R.S. L.SgE 187 



XVIII. On the reduction to a vacuum of the vibrations of an Invariable Pendulum. 

 By Captain Edward Sabine of the Royal Artillery, Secretary of the 

 Royal Society. Communicated by Dr. Thomas Young, Secretary of the 

 late Board of Longitude 207 



Appendix. 



Meteorological Journal kept at the Apartments of the Royal Society, by order of 



the President and Council. 



