Notices  respecting  New  Boohs.  419 
his  death  the  editorship  passed  into  the  hands  of  Messrs.  Abraham 
and  Langevin — two  well-known  investigators  who  have  themselves 
made  important  contributions  to  the  electronic  theory.  The 
arrangement  of  the  matter  is  alphabetical  as  regards  the  authors' 
names,  and  chronological  as  regards  the  contributions  of  each 
author.  At  the  beginning  of  the  book  is  provided  a  table  of 
contents  which  practically  forms  a  subject  index,  a  separate 
author  index  being  provided  at  the  end  of  the  book.  This 
arrangement  greatly  facilitates  the  task  of  finding  any  in- 
formation the  reader  may  be  in  search  of,  and  enhances  the 
value  of  the  book  as  a  work  of  reference. 
It  is  safe  to  say  that  no  worker  in  this  most  fascinating  branch 
of  physics  can  afford  to  be  without  a  copy  of  this  timely  and 
important  publication. 
La  Separation  Elect romagnetique  et  Electro  statique  cles  Minerals. 
Par  Desire  Kokda.  Paris :  L'Eclairage  Electrique.  1905. 
Pp.  219. 
The  subject  of  electromagnetic  separators  is  one  which  has  not 
before  been  treated  in  a  systematic  manner,  and  the  present 
valuable  little  monograph  should  prove  of  considerable  interest 
to  mining  engineers.  The  application  of  purely  electrostatic 
methods  to  the  separation  of  different  kinds  of  ore  is  of  com- 
paratively recent  origin,  and  has  not  as  yet  attained  to  anything  like 
the  importance  which  may  be  claimed  for  electromagnetic  methods. 
The  author  devotes  a  few  pages  to  the  electrostatic  method, 
and  then  gives  a  detailed  account  of  the  practically  important 
electromagnetic  separators.  Then  follow  chapters  on  the  magnetic 
properties  of  minerals  and  the  theory  of  magnetic  separators  ;  the 
treatment  of  the  latter  subject  is  such  as  to  form  an  elementary 
treatise  on  electromaguetism  for  readers  ignorant  of  the  subject, 
with  a  view  to  rendering  the  book  self-contained.  A  good  account 
is  next  given  of  the  various  magnetic  separating  plants  at  present  in 
existence,  and  of  the  results  obtained  with  them.  The  preliminary 
treatment  of  the  ore  before  it  passes  into  the  separator  is  then 
dealt  with,  and  in  a  concluding  theoretical  chapter  the  author  gives 
a  brief  outline  of  paramaguetic  substances  other  than  iron. 
Essais  cles  Materiaucc.  Notions  Fondamentales  Relatives  aiuv 
Deformations  Elastiques  et  Permanentes.  Par  H.  Bouasse, 
Professeur  de  Physique  a  PUniversite  de  Toulouse.  Paris  : 
Gauthier-Villars.     1905.      Pp.  150. 
This  volume  is  the  first  of  a  series  of  small  text-books  to  be 
published  under  the  general  title  of  "  Bibliotheque  de  PEleve 
Ingenieur."  It  deals  in  a  very  general  manner  with  the  theory 
of  straius  and  stresses,  and  with  the  leading  principles  which 
underlie  the  construction  of  various  testing-machines.  It  is  not 
intended  to  be  a  mere  laboratory  guide,  nor  is  any  attempt  made 
to  describe  the  technical  details  of  commercial  testing-machines. 
