CONTENTS op N° 260.— Fourth Series. 



XXI. On the Deadening of the Sounds of Solid Bodies by Internal 

 Resistances. By Dr. E. Warburg page 161 



XXII. Notes on Professor Fleeming Jenkin's Formula. By Thomas 

 T. P. Bruce Warren 169 



XXIII. Popular Difficulties in Tide Theory. By E. Lacy Garbett. 174 



XXIV. On Ocean-currents. — Part II. Ocean- currents in relation 

 to the Physical Theory of Secular Changes of Climate, By James 

 Croll, of the Geological Survey of Scotland , 180 



XXV. On Mica-combinations. By Professor Reusch, of Tubingen. 195 



XXVI. On Criticoids. By Sir James Cockle, F.R.S., the Chief 

 Justice of Queensland, and President of the Queensland Philosophical 

 Society 201 



XXVII. On the Thermal Energy of Molecular Vortices. By W. 

 J. Macquorn Rankine, C.E., LL.D., F.R.SS.L. & E., &c 211 



XXVIII. On Illumination and Polarization in Transparent Sub- 

 stances. By L. Soret 221 



XXIX. On the Organic Dust of the Air. By Augusts De la Rive. 229 



XXX. Proceedings of Learned Societies : — 

 Royal Society : — Dr. J. H. Gladstone on the Refraction- 

 Equivalents of the Elements ^ ..... . 231 



XXXI. Intelligence and Miscellaneous Articles : — 



On Comets and Meteors, by Daniel Kirkwood, LL.D., Professor 



in Indiana University 233 



On a possible Cause of the Gulf-stream, by Robert Gill, Esq.. . 238 



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. 



