CONTENTS 
OF VOL. 157. 
I. Discussion of Tide Observations at Bristol. By T. G. Bunt, Bristol. Communicated 
by the Astronomer Boyal page 1 
II. A Supplementary Memoir on Caustics. By A. Cayley, F.B.S. 7 
III. On the Muscular Arrangements of the Bladder and Prostate , and the manner in 
which the Ureters and Urethra are closed. By James Bell Pettigrew, M.D. 
Edin., First Assistant in the Museum of the Boyal College of Surgeons of Fngl and. 
Communicated by Dr. 'Sharpey, Sec. B.S. 17 
IV. On the Dynamical Theory of Cases. By J. Clerk Maxwell, F.B.S. L.&F. . 49 
V. Fxperimental Besearches in Magnetism and Electricity. By H. Wilde, Esq. Com- 
municated by Dr. Faraday 89 
VI. On the Anatomy of the Fovea Centralis of the Human Betina. By J. W. Hulke, 
F.B. C.S., Assistant Surgeon to the Middlesex and Boyal London Ophthalmic Hos- 
pitals. Communicated by William Bowman, F.B.S 109 
VII. On the Laws of Connexion between the Conditions of a Chemical Change and its 
Amount. By A. Vernon Harcourt, M.A., Student of Christ Church , and Demon- 
strator of Chemistry in the University of Oxford, and William Esson, M.A. , Fellow 
of Merton College , Oxford. Communicated by Sir B. C. Brodie, Bart., F.B.S., 
Professor of Chemistry in the University of Oxford 117 
VIII. Account of Experiments on Torsion and Flexure for the Determination of Bigidities. 
By Joseph D. Everett, D.C.Ij., Assistant to the Professor of Mathematics in the 
University of Glasgow. Communicated by Sir William Thomson, F.B.S. . 139 
IX. On the Structure of the Optic Lobes of the Cuttle-fish. By J. Lockhart Clarke, 
F.B.S., &c. . '. 155 
X. Abstract of the Besults of the Comparisons of the Standards of Length of England, 
France, Belgium, Prussia, Bussia, India, Australia, made at the Ordnance Survey 
Office, Southampton. By Captain A. R. Clarke, B.E., F.B.S., Ac., under the 
Direction of Colonel Sir Henry James, B.E., F.B.S., Ac., Director of the Ordnance 
Survey. With a Preface by Colonel Sir Henry James, B.E., F.B.S., Ac. . 161 
