396  Intelligence  and  Miscellaneous  Articles, 
Formula  for  calculating  column  VIII. : — 
x=  -000238  + -00000306*  --000000026*3. 
The  following  Table  gives  the  results  calculated  by  the  formula 
for  every  fifth  degree  within  the  limits  of  the  experiments  : — 
Difference 
of 
temperature. 
Heat  emitted. 
Ratio  of 
emissive 
power 
of  polished  to 
that  of 
blackened 
surface. 
Polished 
surface. 
Blackened 
surface. 
o 
5 
10 
15 
20 
25 
30 
35 
40 
45 
50 
55 
60 
•000178 
•000186 
•000193 
•000201 
•000207 
•000212 
•000217 
•000220 
•000223 
•000225 
•000226 
•000226 
•000252 
•000266 
•000279 
•000289 
•000298 
•000306 
•000313 
•000319 
•000323 
•000326 
•000328 
•000328 
•707 
•699 
•692 
•695 
•694 
•693 
•693 
•693 
•690 
•690 
•690 
•690 
L.  Intelligence  and  Miscellaneous  Articles. 
ON  CALCULATING-MACHINES.       BY  THOMAS  T.  P.  BRUCE  WARREN. 
TF  we  review  the  history  and  fate  of  the  numerous  contrivances 
-*-  which  have  from  time  to  time  been  proposed  for  economizing 
mental  labour  in  calculating,  we  cannot  be  surprised  on  finding  that 
such  contrivances,  however  perfect,  should  be  suspiciously  regarded, 
and  that  their  adoption  should  be  somewhat  slow. 
The  abacus,  which  is  supposed  to  be  the  invention  of  Pythagoras, 
is  probably  the  earliest  recorded  contrivance  for  calculating  ;  and, 
with  a  trifling  modification,  the  Romans  are  found  to  have  adopted 
it.  The  schwan-pan  of  the  Chinese  may  probably  claim  a  greater 
antiquity  than  either  the  Grecian  or  Roman  abacus. 
The  invention  of  logarithms  by  Napier  proved  an  inestimable  boon 
to  computers.  Analogous  to  Napier's  rods  are  the  different  forms  of 
sliding- rules  now  in  use. 
Pascal's  machine,  although  deficient  in  speed  and  accuracy,  is  said 
to  contain  the  germ  which  has  characterized  all  the  later  machines 
of  the  same  class,  namely  those  which  give  their  results  by  the 
purely  mechanical  action  of  geared  wheels,  levers,  or  friction-rollers. 
During  the  seventeenth  and  eighteenth  centuries  we  find  the 
names  of  Leibnitz,  Grillet,  and  Sir  Samuel  Moreland  amongst 
others  who  directed  their  attention  to  the  production  of  calculating 
machines,  which  either  obviated  some  of  the  disadvantages  in  the 
machine  of  Pascal,  or  possessed  new  features  in  their  application  to 
special  operations. 
