CONTENTS  of  N°  281.— Fourth  Series. 
XL.  On  the  Reflection  and  Refraction  of  Light  by  intensely  Opaque 
Matter.     By  the  Hon.  J.  W.  Strutt,  M.A.,  late  Fellow  of  Trinity 
College,  Cambridge    page 
XLI.  Reply  to  Professor  Clausius.     By  P.  G.  Tait 
XLII.  On  Hamilton's  Principle  and  the  Second  Proposition  of  the 
Mechanical  Theory  of  Heat.     By  C.  Szily   
XLIII.  Note  on  Recurrent  Vision.     By  Professor  C.  A.  Young,  of 
Dartmouth  College 
XLIV.  On  the  Origin  of  the  Earth's  Magnetism,  and  the  Magnetic 
Relations  of  the  Heavenly  Bodies.     By  F.  Zollner     
XLV.  On  a  Bicyclic  Chuck.     By  A.  Cayley,  F.R.S 
XLVI.  On  a  Collector  for  Frictional  Electrical  Machines.     By  Dr. 
H.  Emsmann    3 
XLVII.  On  Electrolysis,  and  the  Passage  of  Electricity  through 
Liquids.     By  G.  Quincke 3 
XLVIII.  Notices  respecting  New  Books : — An  Elementary  Trea- 
tise on  Curve-Tracing.  By  Percival  Frost,  M.A. — Arithmetic  in 
Theory  and  Practice.  By  J.  Brook  Smith,  M.A.,  LL.B. — Kuklos,  an 
Experimental  Investigation  into  the  Relationship  of  certain  Lines. — 
Part  I.  By  John  Harris 376-3 
XLIX.  Proceedings  of  Learned  Societies : — 
Royal  Society  : — Dr.  W.  Huggins  on  the  Spectrum  of  Encke's 
Comet ;  Mr.  G.  Gore  on  Fluoride  of  Silver ;  Messrs.  De  La 
Rue,  B.  Stewart,  and  B.  Loewy  on  some  recent  Researches 
in  Solar  Physics,  and  a  law  regulating  the  time  of  duration 
of  the  Sun-spot  Period ;  Dr.  W.  Huggins  on  the  Telescopic 
Appearance  of  Encke's  Comet ;  Mr.  D.  M'Farlane's  Expe- 
riments made  to  determine  Surface-conductivity  for  Heat  in 
Absolute  Measure     380-3 
L.  Intelligence  and  Miscellaneous  Articles : — 
On  Calculating-machines,  by  Thomas  T.  P.  Bruce  Warren  .... 
On  a  new  method  of  Measuring  the  Velocity  of  Rotation,  by 
Professor  A.  E.  Dolbear 3 
Preliminary  Note  on  a  remarkable  fact  observed  on  the  Contact 
of  certain  Liquids  of  very  different  superficial  Tensions,  by  G. 
van  der  Mensbrugghe 3 

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