Re: Temperature Scales

[Rick Strickert <rick_strickert@URSCORP.COM>]

Herbert H Gottlieb wrote:
> Does anyone on this list have an historical reference
> that give greater details concerning the origin of the
> Fahrenheit thermometer scale?

The following is from the phys-l archive reference I noted  yesterday and
includes references at the end:

 Ole Christensen Roemer (1644-1710) was a contemporary (and friend) of
 Isaac Newton and best remembered for his (controversial for many years)
 discovery of the finite speed of light (a story in itself).  However,
 Roemer was a most versatile person (with accomplishments covering more
 than a dozen different careers in his native Denmark!).  But Ole had
 another under-recognized accomplishment.

 It was Roemer who designed and constructed his own more accurate
 thermometers and was the first to realize and use *two* fixed points
 (rather than one) to calibrate the scale of a thermometer.  Roemer's
 upper point was the boiling point of water, which he set as 60 degrees.
 (Roemer apparently did not realize that water's b.p. depended on
 atmospheric pressure, a fact that Fahrenheit later discovered.)

 Roemer's lower calibration point has been the subject of some debate.
 Some have said that a 0 value was assigned to a mixture of water, ice,
 and ammonium chloride; others claimed Roemer used the melting point of
 snow (which he marked as 7.5 deg.).  Because many of Roemer's records
 were destroyed in a fire in Copenhagen in 1728, we may never know for
 sure. (BTW, 7.5 is one-eighth of 60, and accurately dividing a scale on
 a thermometer by powers of 2 is easily accomplished with simple tools
 of that day.)

 In 1708, the German physicist, Daniel Gabriel Fahrenheit (not "Gabriel
 Daniel"), visited Ole Roemer in Copenhagen.  Roemer showed him the
 two-point calibration system he had developed.  Roemer was also testing
 small thermometers designed for meteorological use which had divisions
 marked from 0 to 22.5 deg. (normal blood temperature) using Roemer's
 scale.

 Fahrenheit was so impressed with Roemer's thermometers and the two-point
 calibration scale that he adopted them for use back in Germany.  While
 it appears that Fahrenheit used the same lower calibration point as that
 of Roemer, it is clear (from a letter written by Fahrenheit to Boerhaave
 in 1729 and rediscovered in 1936) that Fahrenheit used Roemer's 22.5 deg
 ("normal body temperature") as the upper point.  From a 1724 paper,
 Fahrenheit determined the upper point either in the mouth or under the
 armpit (the third alternative technique was not noted :-)).  It is not
 clear whether Fahrenheit (or Roemer) distinguished a male or female body
 temperature (in his Latin paper Fahrenheit used the word "hominis").

 Fahrenheit later multiplied Roemer's scale numbers by four for easier
 reading.  This made the melting point of ice 30 deg. and body
 temperature 90 deg.

 Eventually Fahrenheit adjusted the calibration points to 32 (ice melting
 point) and 96 (body temperature) to simplify marking the scale divisions
 (i.e., 64 divisions).  Thus the boiling point of water would be measured
 experimentally near 212 deg.  Later, the b.p. of water, at one
 atmosphere pressure, was used as the upper calibration point of 212,
 returning to Roemer's initial calibration concept.  (With these two
 calibration points, the experimentally determined temperature of a
 healthy person is now approximately 98.6 deg.)

 Thus, as noted by historian I.B. Cohen, Ole Roemer's thermometer scale
 design is really the basis of the thermometer scale used by Daniel
 Gabriel Fahrenheit (1686-1736).

 For more information on Roemer, the thermometer, and his other
 accomplishments, see _Roemer and the First Determination on the Velocity
 of Light_, I. Bernard Cohen (Burndy Library, New York, 1944).  Cohen's
 short book has many references, mostly in Danish, French, German, or
 Latin; and mostly very old. See also, D.G.Fahrenheit, Phil. Trans. Roy.
 Soc. London, 33, 78 (1724).  Fahrenheit's own acknowledgement of
 Roemer's contribution is in a letter he wrote in 1729 and reprinted in
 _Kon. Akad. Wet. Verhand._, Vol.xvi, 1936, pp.1-37. Also Z.  Kopal notes
 Roemer's contribution in _Dictionary of Scientific Biography_, ed.  C.C.
 Gillispie (Scribners, NY, 1975), Vol. 11, p.525.  A more recent
 discussion of Roemer's temperature scale was given by Robert H.  Romer,
 "Temperature scales: Celsius, Fahrenheit, Kelvin, Reamur, and Romer",
 _The Physics Teacher_, 20 (Oct. 1982), pp.450-454).

 If you're extremely adventurous, you can peruse a bibliography on Roemer
 by Per Friedrichsen, "Dansk Astronomi Gennem Firhundrede Ar", Bind 3,
 ISBN 87 7245 281 1, Produktion Rhodos, 1990; or stop by the Ole Roemer
 Museum in Taastrup, Denmark.



 Rick Strickert
 URS Radian
 Austin, TX