150  Notices  respecting  New  Books. 
without  reference  to  details  of  manipulation,  and  in  few  cases,  if  in 
any,  is  an  experiment  described  for  purposes  of  mere  illustration. 
The  contents  of  the  volume  are  as  follows  : — After  an  introduc- 
tion there  are  two  chapters  on  Thermometry  and  Calorimetry  (the 
registration  of  temperature  and  the  measurement  of  Heat),  in  which 
these  subjects  are  very  fully  treated,  the  latter  chapter  containing 
the  definitions  of  Thermal  Capacity,  Specific  Heat,  and  Latent  Heat. 
Then  follows  a  statement  of  the  elementary  principles  of  Dynamics, 
and  of  the  principles  of  the  measurement  of  Internal  Forces.  From 
this  point  begins  the  exposition  of  the  principles  of  Thermodyna- 
mics. One  chapter  (ch.  6)  contains  an  account  of  isothermal  lines, 
in  the  course  of  which  a  pretty  full  account  is  given  of  Dr.  Andrew's 
experiments  in  illustration  of  the  continuity  of  the  gaseous  and  liquid 
states;  a  second  (ch.  7),  of  adiabaiic  lines  ;  a  third  (ch.  8)  is  devoted  to 
Sadi  Carnot's  Heat  Engine  and  its  four  operations,  which  are  explained 
by  means  of  the  indicator  diagram,  and  lead  up  to  the  definitions  of 
a  Cycle,  of  Efficiency,  and  of  the  Absolute  Scale  of  Temperature. 
Then  follow  seven  chapters  of  applications.  The  subjects  now  indi- 
cated occupy  about  two  thirds  of  the  work ;  the  remaining  part  is 
mainly  taken  up  with  the  subjects  of  radiation  and  conduction,  and 
ends  with  a  most  interesting  chapter  on  the  molecular  theory  of 
the  constitution  of  bodies.  In  the  course  of  the  work  there  are  dis- 
cussions on  several  subjects  not  hitherto  mentioned,  which  deserve 
notice  as  being  original  in  treatment,  or  as  not  commonly  given  in 
elementary  books ;  such  are  : — the  account  of  Watt's  Indicator  and 
its  application  to  Thermodynamics  (p.  102  .. .  ),  the  discussion  of 
the  Intrinsic  Energy  of  a  system  of  bodies  (ch.  12),  the  account  of 
the  determination  of  heights  by  the  barometer  (ch.  14),  that  of  the 
propagation  of  Waves  by  Longitudinal  Disturbances,  (ch.  15),  of 
Fourier's  Theory  of  the  conduction  of  Heat  (p.  236 ... ),  and  the 
chapter  (ch.  20)  on  Capillarity. 
The  above  account  will  perhaps  convey  a  not  altogether  inade- 
quate notion  of  the  contents  of  Mr.  Clerk  Maxwell's  book.  If  it 
were  compared  chapter  by  chapter  with  any  of  the  existing  elemen- 
tary manuals,  such  as  Mr.  Balfour  Stewart's,  it  would  be  seen  that 
it  treats  with  brevity  what  is  ordinarily  given  at  full  length,  and  am- 
plifies what  is  in  most  cases  cut  short.  The  parts  on  which  Mr. 
Clerk  Maxwell  mainly  dwells  are  those  presenting  the  greatest  diffi- 
culty to  the  learner.  This  difficulty  is  inherent,  and  would  remain 
very  great  even  wrere  the  subject  treated  by  a  writer  who  possessed 
in  the  highest  degree  the  art  of  exposition.  But  whatever  the  causes, 
whether  choice  of  subject  or  mode  of  treatment,  there  can  hardly 
be  a  doubt  that  the  book  will  severely  task  the  attention  of  the 
reader  who  comes  fresh  to  the  subject ;  and  this  we  fear  will  greatly 
limit  its  usefulness  as  a  book  "adapted  for  the  use  of  Artisans  and 
Students  in  Public  Schools."  Considered,  however,  as  addressed  to 
students  already  well  trained  in  something  more  than  the  elements 
of  mathematics,  and  familiar  with  the  fundamental  laws  of  mechanics, 
it  would  be  hard  to  name  a  better  book.  To  such  readers  it  will 
prove  an  excellent  introduction  to  the  very  difficult  science  of  Ther- 
