CONTENTS  OF  VOL.   XF. SIXTH   SERIES.  Ml 
Page 
Mr.    E.    Buckingham  :     Elementary  Notes    on    Thermody- 
namics :  the  Plug  Experiment 678 
Lord    Rayleigh  on    some  Measurements  of    Wave-Lengths 
with  a  Modified  Apparatus 085 
Mr.  J.  W.  Nicholson  on  the  Symmetrical  Vibrations  of  Con- 
ducting Surfaces  of  Revolution    703 
Prof.  H.  Becquerel  on  some  Properties  of  the  a  Rays  emitted 
bv  Radium  and  by  Bodies  rendered  Active  by  the  Radium 
Emanation 722 
Notices  respecting  New  Books  : — 
Dr.  Hans  Witte's  Ueber  den  gegenwartigen  Stand  der 
Erage  nach   einer  mechanischen  Erklarung  der  elek- 
trischen  Erscheinungen     728 
Intelligence  and  Miscellaneous  Articles  : — 
On  a  Mercury-sealed  Tap,  by  A.  P.  Chattock 728 
NUMBER  LXVL— JUNE. 
Prof.  J.  S.  Townsend  on  the  Eield  of  Eorce  in  a  Discharge 
between  Parallel  Plates     729 
Dr.  E.  S.  Johonnott  on  the  Black  Spot  in  Thin  Liquid  Films  74(5 
Prof.  W.  H.  Bragg  on  the  a  Particles  of  Uranium  and  Thorium  754 
Prof.  J.  J.  Thomson  on  the  Number  of  Corpuscles  in  an  Atom  769 
Prof.  R.  W.  Wood  on  Eluorescence  and  Lambert's  Law  ....  7S2 
Prof.  A.  Anderson  on  the  Eocometry  of  Concave  Lenses  and 
Convex  Mirrors     789 
Prof.  H.  A.  Wilson  on  the  Velocities  of   the  Ions  of  Alkali 
Salt  Vapours  at  High  Temperatures    790 
Dr.  O.  Hahn  on  some  Properties  of  the  u  Rays  from  Radio- 
thorium  793 
Dr.  H.  L.  Bronson  on  the  Ionization  produced  by  a  Ravs    .  .  80(> 
Dr.  C.  Gr.  Barkla  on  Secondary  Rontgen  Radiation   ........  812 
Mr.  A.  A.  C.  Svvinton  on  an  Experiment  with  the  Electric  Arc  829 
Notices  respecting  New  Books  : — 
Cambridge    Tracts   in    Mathematics    and    Mathematical 
Physics,  Nos.  1  &  2 831 
Prof.   Carslaw's  Introduction  to  the   Infinitesimal   Cal- 
culus ;    and   A.  H.   Angus's    Preliminary    Course    in 
Differential  and  Integral  Calculus    .    832 
E.  Picard's  G^uvres  de  Charles  Hermite     833 
Dr.   O.    Biermann's    Vorlesungen    iiber    Mathematische 
Niihermethoden      833 
W.  B„  Erankland's  The  First  Book  of  Euclid's  Elements  833 
Dr.  Hudson's  Rummer's  Quartic  Surface 834 
J.  Gruillaume's  Notions  d'Electricito    834 
Index , 835 
