VI CONTENTS OF VOL. XLVII. FOURTH SERIES. 



Page 

 Proceedings of the Geological Society : — 



Prof. E. Hull on the Permian Breccias and Boulder-beds 



of Armagh 313 



Mr. G. W. Stow's Geological Notes on Griqualand West. 313 

 Prof. T. E. Jones on some Bivalve Entomostraca, chiefly 



Cypridinidae, of the Carboniferous formations 314 



On the Permanent Magnetism of Steel, by E. Bouty 315 



Contribution to the Theory of the Magnetic Forces, by-M. Stefan. 318 

 On a peculiar Occurrence of Crystallized Silicic Acid, by Theodor 



Hiibener * 319 



On the Spectrum of the Light of Exploding Gun-cotton, by 



O. Lohse 319 



Dr. J. H. v. Madler 320 



NUMBER CCCXIIL— MAY. 



M. G. Quincke on the Determination of the prime Angle of 

 Incidence and prime Azimuth for the different Eraunhofer's 



Lines 321 



Mr. T. Muir on Sylvester's and other forms of continued 



Fraction for Circle-quadrature 331 



Mr. J. Dewar on the Physical Constants of Hydrogenium . . 334 

 M. E. Kohlrausch on the Absolute Value of the Siemens 

 Mercury Unit of Electrical Resistance. (With a Plate.) . . 342 



Direct Solution of a Geometrical Problem , 354 



Captain J. Herschel on a new form of Calendar, by which the 

 Year, or Month, or Month-day, or Week-day maybe readily 

 found when the other three components of a date are given. 357 

 Dr. W. B. Carpenter on the Physical Cause of Ocean-currents. 359 

 M. E. Kohlrausch on a Variation-Barometer. (With a Plate.) 362 

 Notices respecting New Books : — 



Prof. P. G. Tait's Elementary Treatise on Quaternions . . 364 

 Mr. T. Muir on the Expression of a Quadratic Surd as 



a continued fraction 366 



Mr. R. A. Proctor on the Universe and the Coming Tran- 

 sits 367 



Mr. C. C. Reeks's Elementary Astronomy 374 



Proceedings of the Royal Institution : — 



Professor Tyndall on the Acoustic Transparency and Opa- 

 city of the Atmosphere 374 



Proceedings of the Royal Society : — 



Mr. J. N. Lockyer's Researches in Spectrum- Analysis in 



connexion with the Spectrum of the Sun. — Part III. . . 384 

 Mr. J. Clerk Maxwell on Double Refraction in a Viscous 



Eluid in motion 390 



Calorific Effects of the Magnetism in an Electromagnet with 

 several Poles, by A. Cazin 392 



