CONTENTS op N° 231.— Fourth Series. 



XLII. Researches in British Mineralogy. By David Fokbes, 

 F.R.S. &c page 329 



XLIII. A new Attempt to determine the Resultant of two Pressures 

 on a Fixed Point. By G. W. Keely, Esq 354 



XLIV. On the Colour of the Clouds and Sky. By H. C. Sorby, 

 F.R.S 356 



XLV. An Inquiry into the Evidence on which the Theory of the 

 Circulation of the Atmosphere is based. By J. Knox Laughton, 

 B.A., R.N 359 



XL VI. On Isoperimetric Regular Polygons. By W. J. Macquorn 

 Rankine, C.E., LL.D., F.R.SS.L. & E. &c 365 



XLVII. A Contribution to Electrodynamics. By Bernhard Rie- 



MANN 368 



XLVIII. On the Velocity of Atomic Motion. By Dr. Alexander 



Naumann 373 



XLIX. On the Figure of the Bullet which experiences the least 

 resistance from the Air. By Francis A. Tarleton, Fellow and 



Tutor, Trinity College, Dublin 377 



L. On the Approximate Rectification of Circular Arcs. By W. 



J. Macquorn Rankine, C.E., LL.D., F.R.SS.L. & E. &c 381 



LI. Contribution to the Mechanical Theory of the Electrical Cur- 

 rent. By Dr. Gerlach 382 



LII. Proceedings of Learned Societies : — 



Royal Society : — SirW. Thomson on a Self-acting Apparatus 

 for multiplying and maintaining Electric Charges, with Appli- 

 cations to illustrate the Voltaic Theory 391-396 



Geological Society: — Mr. H. B. Medlicott on the Alps 

 and the Himalayas ; Mr. D. Mackintosh on the Terminal 

 Curvature of Slaty Laminae in West Somerset ; Messrs. P. M. 

 Duncan and J. Thomson on Cyclocyathus ; Dr. Dawson 

 on a new Pulmonate Mollusk ; Mr. J. W. Salter on some 

 tracks of JPteraspis (?) in the Upper Ludlow Sandstone, and 

 on a new Lingulella from the red Lower Cambrian Rocks of 

 St. David's ; Mr. G. Busk on the Dentition of Fossil Bears ; 

 Dr. J. Haast on the Geology of the Province of Canterbury, 

 New Zealand ; the Rev. J. H. Timins on the Chemical Geo- 

 logy of the Malvern Hills ; Mr. T. M. Hall on the Relative 

 Distribution of Fossils throughout the North Devon series ; 

 Mr. W. R. Swan on the Geology of the Princess Islands ; Mr. 

 C. Collingwood on the Sulphur Springs of Northern For- 

 mosa ; Mr. G. B. Stacey on the Geology of Benghazi ; Mr. E. 

 Thornton on the Existence of large Coal-fields in the Pro- 

 vince of St. Catherine's, Brazil ; Mr. G. Maw on the White 

 Clays of the Lower Tertiaries ; Mr. S. V. Wood, Jun., on the 



Postglacial Structure of the South-east of England 396-403 



LIII. Intelligence and Miscellaneous Articles: — 



Investigations on the Influence of Heat on the Mechanical Force 



of Frogs' Muscle, by M. Chmoulevitch . . 403 



On the Intensity of the Solar Radiation, by M. J. L. Soret . . . 404 

 On System in Mineralogical Nomenclature, by J. D. Dana. ... 407 



It is requested that all Communications for this Work may be addressed, 

 post-paid, to the Care of Messrs. Taylor and Francis, Printing Office, Red 

 Lion Court, Fleet Street, London. 



