the  Mechanical  Theory  of  Heat.  Ill 
due  to  Clausius,  who  published  his  demonstration  of  it  in  the 
month  of  May  last  year,  in  the  second  part  of  his  paper  on  the 
Motive  Power  of  Heat." 
In  spite  of  these  utterances  by  W.  Thomson,  Mr.  Maxwell 
has  thought  proper  to  leave  my  writings  unmentioned.  He  cir- 
cumstantially explains  (pp.  145-155)  that,  in  an  essential  point, 
Carnot  was  in  error  in  his  considerations,  and  that  consequently 
the  proposition  expressed  by  him,  as  well  as  his  demonstration 
of  it,  required  to  be  altered;  yet  in  all  this  he  cannot  find  a 
single  word  in  order  to  state  who  it  was  that  made  those  altera- 
tions,  and  correctly  expressed  the  second  theorem  of  the  mecha- 
nical theory  of  heat,  and  reduced  it  to  true  principles. 
Besides,  W*  Thomson,  in  his  memoir,  when  speaking  of  my 
demonstration,  says*: — "The  following  is  the  axiom  on  which 
Clausius's  demonstration  is  founded  : — It  is  impossible  for  a  self- 
acting  machine,  unaided  by  external  agency,  to  convey  heat  from 
one  body  to  another  at  a  higher  temperature"  The  proposition 
here  printed  in  italics  is  in  Mr.  Maxwell's  book  (p.  153)  quoted  in 
exactly  the  same  words  in  which  Thomson  has  clothed  it;  but 
here,  instead  of  the  introductory  words  "The  following  is  the 
axiom  on  which  Clausius's  demonstration  is  founded,'-' we  have: — 
"  Carnot  expresses  this  law  as  follows."  Thus,  while  in  the  re- 
mainder of  the  quotation  Thomson's  words  are  used,  my  name  is 
replaced  by  that  of  Carnot,  without  a  word  of  explanation  for 
the  alteration.  This  is  so  mysterious  to  me,  that  I  cannot  help 
supposing  there  must  be  a  misprint.  However,  of  course  I  must 
leave  it  to  Mr.  Maxwell  to  clear  up  the  matter. 
Out  of  the  detailed  statements  which  follow  the  above,  I  will 
only  call  attention  to  two  passages. 
The  result  above  mentioned,  and,  on  account  of  its  importance, 
often  spoken  of  by  others,  viz.  that  saturated  steam  has  a  nega- 
tive specific  heat,  is  cited  by  Maxwell  in  the  following  manner: — 
"  It  appears,  from  the  experiments  of  M.  Regnault,  as  shown  in 
the  diagram  at  p.  135,  that  heat  leaves  the  saturated  steam  as 
its  temperature  rises,  so  that  its  specific  heat  is  negative." 
In  reference  to  my  way  of  calculating  the  density  of  saturated 
steam,  from  which  have  resulted  considerable  deviations  from 
Mariotte  and  Gay-Lussac's  law,  and  which  was  first  adopted  by 
Eankine  and  Thomson  much  later,  Maxwell  says: — "In  the 
meantime  Rankine  has  made  use  of  the  formula  [the  same  that 
I  have  used]  in  order  to  calculate  the  density  of  saturated  steam." 
An  intention  on  the  part  of  Mr.  Maxwell  to  suppress  my  name 
could,  I  think,  hardly  be  more  distinctly  apparent  than  in  these 
passages. 
All  the  quotations  above  given  referred  to  my  first  memoir  on 
*  LI  cc.  pp.  266  et  14. 
