CONTENTS 
XII. The Bakerian Lecture. — On the Theoretical Explanation of an apparent 
new Polarity in Light. By G. B. Airy, Esq., M.A., F.R.S., Astronomer 
Royal page 225 
XIIL On the Nervous System. By Sir Charles Bell, F.R.S., &;c 245 
XIV. Researches on the Tides. — Twelfth Series. On the Laws of the Rise and Fall 
of the Sea's Surface during each Tide. By the Rev. W. Whewell, B.D . , F.R.S. , 
Fellow of Trinity College, Cambridge 255 
XV. Contributions to the Chemical History of Archil and of Litmus. By Robert 
Kane, M.D., M.R.l.A. Communicated by Francis Baily, Esq., V.P.R.S., fyc. 
8$c. 8$c. . 273 
XVI. On the influence of Iodine in rendering several Argentine Compounds, spread 
on Paper, sensitive to Light, and on a new Method of producing, with greater 
distinctness, the Photographic Image. By Mr. Robert Hunt. Communicated 
by Sir J. F. W. Herschel, Bart., K.H., V.P.R.S., 8$c. 8$c. 8$c. . . . 325 
XVII. Description of an Escapement for an Astronomical Clock, invented by the late 
Captain Henry Kater, F.R.S. , 8$c., drawn up from his own Memorandums by 
his Son Edward Kater, Esq. Communicated by Sir J. F. W. Herschel, 
Bart., K.H., V.P.R.S., &;c. 8$c. &;c 335 
XVIII. On the Constitution of the Resins. Part IV. By James F. W. Johnston, Esq., 
M.A., F.R.S., Professor of Chemistry and Mineralogy in the University of 
Durham 34 1 
XIX. On the Constitution of the Resins. Part V. By James F. W. Johnston, Esq., 
31. A., F.R.S., Professor of Chemistry and 31ineralogy in the University of 
Durham 361 
XX. Experimental Researches on the Strength of Pillars of Cast Iron, and other 
Materials. By Eaton Hodgkinson, Esq. Communicated by Peter Barlow, 
Esq., F.R.S., 8$c 385 
