420  Notices  respecting  New  Books. 
The  task  accomplished  by  the  author  is,  indeed,  a  much  more 
formidable  one,  and  much  more  likely  to  be  useful  to  the  reader 
than  a  purely  descriptive  work.  The  treatment  is  characterized 
by  vigour  and  freshness  combined  with  clearness.  To  a  large 
extent  the  author's  method  is  based  on  a  study  of  the  stress-strain 
diagram  and  its  characteristics  in  various  cases.  No  very  advanced 
mathematical  methods  are  used,  although  the  reader  is  assumed  to 
have  a  knowledge  of  the  calculus  and  of  the  simpler  forms  of 
differential  equations.  The  subject  is  throughout  approached 
from  the  purely  physical  rather  than  technical  standpoint,  and 
the  rough-and-ready  methods  of  the  purely  technical  man  come 
in  for  a  good  deal  of  severe  comment.  "We  could  desire  no  better 
introduction  to  the  difficult  subject  of  strains  and  stresses  than 
this  masterly  exposition,  which  augurs  well  for  the  success  of  the 
new  series  of  text-books. 
Elelctromagnetische  Schwingungen  and  Wellen.  Von  Dr.  Josef 
Bitter  ycxn"  Geitler,  a.  o.  Professor  der  Physik  an  der  K.K. 
Deutschen Universitat,  Prag.  Mit  86  eingedruckten  Abbildungen. 
Braunsckweig  :  P.  Vieweg  und  Sohn.     1905.     Pp.  viii  +  154. 
This  monograpk  forms  No.  6  of  tke  series  entitled  Die  Wissenschaft, 
now  in  course  of  publication.  Tke  subject  of  electromagnetic 
waves  has  always  had  a  singular  fascination  for  all  interested  in 
the  development  of  physical  science,  and  the  simple  and  clear 
non-mathematical  account  of  it  contained  in  the  monograph  under 
review  should  appeal  to  a  very  wide  circle  of  readers.  The  author 
deals  with  the  subject  in  the  order  of  its  historical  development, 
beginning  with  a  brief  review  of  the  old  action- at-a-distauce 
theories,  Faraday's  ideas  regarding  strains  and  stresses  in  a 
medium,  Clerk  Maxwell's  brilliant  theoretical  developments  of 
those  ideas,  and  their  practical  realization  in  the  epoch-making 
discoveries  of  Hertz.  The  remaining  half  of  the  volume  deals 
with  the  methods  of  detecting  electromagnetic  waves,  with  their 
relation  to  light  waves,  and  with  their  practical  applications  in 
wireless  telegraphy. 
Dr.  J.  Fricl-s  l^IiysiL-aliscJie  Technik.  Siebente  vollkommen  umge- 
arbeitete  und  stark  vermehrte  Aunage  von  Dr.  Otto  Lehmaxn, 
Professor  der  Physik  an  der  techuiscken  Hockschule  in 
Karlsruhe.  ErsterBand:  Zweite  Abteilung.  Mit  1905  in  den 
Text  eingedruckten  Abbildungen.  Braunsckweig  :  F.  Vieweg 
und  Sokn.     1905.     Pp.  xx  +  1002. 
Some  time  ago  we  had  occasion  to  review  Part  I.  of  Vol.  I.  of  this 
valuable  work,  and  now  Part  II,  completing  the  volume,  is 
before  us.  The  subjects  dealt  with  are  measurements  of  length, 
mass,  and  time  ;  various  forms  of  apparatus  illustrating  the  laws  of 
statics  ;  experiments  on  the  general  properties  of  solids,  liquids, 
and  gases;   the  measurement  of  temperature  and  construction  of 
