T H A C H E R ' s   SLIDE RULE                         Model » 4012 «
*********************************************************************
Keuffel & Esser, NewYork / USA  (1917)                      SN = 4689

Edwin Thacher ( 1839-1920 ), an  USA  engineer ( well  known  for its
work on  reinforced concrete  constructions ),  was  the  inventor of
this  ingenious  cylindrical logarithmic  slide rule  with  a  "real"
length of 30 feet  ( ~ 9 Meter )  -  giving a precision of  5 digits.
It  was  patented  in  1881 and  build & marketed  by K & E, NewYork. 


S C A L E   C O N F I G U R A T I O N   OF THE  THACHER's  SLIDE RULE
=====================================================================
The 30' scales are  segmented in 18" scales  having  2 portions each:

 An  EXTERNAL  Segmented  Cylinder  that  rotates  with  Scales ...

  UP LOOKING ------------------------------------------- LOOKING UP

   |      LEFT-C  =  sqrt(X)   if  X  has ODD  No. of Digits     |
   |     RIGHT-C  =  sqrt(X)   if  X  has EVEN No. of Digits     |
   |           B  =  X                               20 Segments |
   ===============================================================
   |           A  =  X                               20 Segments |
   +-------------------------------------------------------------+
 O== A movable INTERNAL Cylinder that also rotates w. Scales ... ==O
   +-------------------------------------------------------------+
   |           A' =  X'  ( 9" left-shifted X )       20 Segments |
   ===============================================================
   |           B' =  X'  ( 9" left-shifted X )       20 Segments |
   |     RIGHT-C' =  sqrt(X')  if  X' has EVEN No. of Digits     |
   |      LEFT-C' =  sqrt(X')  if  X' has ODD  No. of Digits     |

  DOWN LOOKING --------------------------------------- LOOKING DOWN


The  THACHER's came in a  MAHOGANY BOX  with a 72 p.INSTRUCTION BOOK.

         A   C O P Y   of this  INSTRUCTION BOOK  can be found in ...

         http://sliderulemuseum.com/SR_Library_British.htm

Remark(1) THACHER's Model 4013 has a MAGNIFYER-"Cursor" (s.BookCover)

REMARK(2) Compare & ADMIRE the Simplizity of the  ATLAS CIRCULAR  ...

                       Historical Remarks ...
impressum:
*********************************************************************
© C.HAMANN        http://public.BHT-Berlin.de/hamann         06/13/11