V CONTENTS OF VOL. L. FOURTH SERIES. 



Page 

 Proceedings of the Boyal Society : — 



Mr. J. Norman Lockyer on a New Map of the Solar 

 Spectrum 144 



Prof. J. Tyndall on Acoustic Eeversibility 146 



Proceedings of the Geological Society : — 



Prof. H. A. Nicholson on species of Ohcetetes from the 



Lower Silurian Rocks of North America 152 



Mr. L. C. Miall on the composition and structure of the 



Bony Palate of Ctenodus 152 



The Eev. P. B. Brodie on a Eailway Section of the Lower 

 Lias and Ehsetics between Stratford-on-Avon and 



Fenny Compton . -. 153 



Mr. H. G. Seeley on the Eesemblances of Ichthyosaurian 

 Bones to the Bones of other Animals ; on the Eesem- 

 blances of Plesiosaurian Bones to the Bones of other 

 Animals ; on the Tibia of Megalornis ; on Cervical and 



Dorsal Vertebrae of Crocodilus cantabrigiensis 153 



Mr. H. G. Seeley on the base of a large Lacertian Skull 

 from the Potton Sands ; on a Section through the Devo- 

 nian Strata of West Somerset ; and on the Pectoral 



Arch and Fore Limb of Ophthalmosaurus 154 



On the Temperature of the Sun, by J.-B. Soret 155 



On Fused Boracic Acid and its Tempering, by V. de Luynes. 158 

 On the discovery of a method of obtaining Thermographs of the 

 Isothermal Lines of the Solar Disk, by A. M. Mayer .... 159 



NUMBER CCCXX.X.— SEPTEMBEE. 



Mr. H. A. Eowland on Kohlrausch's Determination of the 



Absolute Value of the Siemens Mercury Unit of Electrical 



Eesistance 161 



Mr. E. H. M. Bosanquet on Temperament, or the Division 



of the Octave.— No 164 



Mr. M. Merriman on the Flexure of Continuous Girders . . 179 

 Prof. E. Clausius on the Theorem of the Mean Ergal, and its 



Application to the Molecular Motions of Gases 191 



Mr. E. Mallet on the Origin and Mechanism of production of 



the Prismatic (or columnar) Structure of Basalt 201 



Sir W. Thomson on an Alleged Error in Laplace's Theory of 



the Tides 227 



Mr. J. Croll on the ' Challenger's ' Crucial Test of the Wind 



and Gravitation Theories of Oceanic Circulation 242 



Prof. P. E. Chase on the Cosmical Activity of Light 250 



On a Property of an Electrized Water-surface, by G. Lipmann. 254 

 On the Influence of the Texture of Iron upon its Magnetism, by 



L. Kiilp, of Darmstadt 255 



On Magnets formed from Compressed Powders, by J. Jamin. 255 



