IV 



CONTENTS. 



Part III. 



PAar. 



N°. XVII. O-v the Intensity of Light in the neighbourhood of a Caustic: i^ Georgk 



BiDDELL AiHY, Esq. M.A 379 



XVIII. On the Rejlexion and Refraction of Sound: by G. Gkeen, Esq 403 



XIX. On a new Genus of Fossil Mnttilocular Shells, found in the Slate-Rocks 



of Cormvall : by D. T. Ansted, B.A 415 



XX. On a Question in the Theory of Probabilities: by Augustus De 



Morgan, Esq 423 



XXI. On the Diffraction of an Object-glass loith a triangular Aperture : by 



the Rev. S. Earnshaw, M.A 43 1 



XXII. On the Decrement of Atmospheric Temperature depending on the Height 



above the Earth's Surface: by the Rev. J. Challis 443 



XXIII. 0« the Motion of Waves in a variable Canal of small Depth and Width: 



by George Green, Esq. B.A 457 



XXIV. On the Theory of the Equilibrium of Bodies in Contact : by the Rev. H. 



MosELE Y, M.A 46'3 



XXV. Account of Observations of Halley's Comet : by R. W. Rothman, Esq. 



M.A \ 493 



XXVI. Mathematical Investigation of the Effect of Machinery on the Wealth of 

 a Community in which it is employed, and on Ike Fund for the Pay- 

 ment of Wages : by John Tozer, Esq. B.A ."SO? 



XXVII. Novilia; Flora; Maderensis: or Notes and Gleanings of Maderan Botany: 



by the Rev. R. T. Lowe, M.A 523 



XXVIII. On a New Correction in the Construction of the Double Achromatic 



Object-glass : by Richard Potter, Esq. B.A 553 



XXIX. A Statistical Report of Addenbrooke's Hospital, for the Year 1837: by 



Henry J. H. Bond, M.D 565 



ADVERTISEMENT. 



2^HE Society as a body is not to be considered responsible for any 

 focts and opinions advaticed in the several Papers, which must rest 

 entirely on the credit of their respective Authors. 



The Society takes this opportunity of expressing its grateful 

 acknowledgments to the Syndics of the University Press, for tlieir 

 liberality in taking upon themselves the expense of printing this 

 Part of its Transactions. 



