The data in the file forbes.dat is taken from Weisberg (1985), who
took them from an 1857 paper by a Scottish physicist, James D. Forbes.
The measurements are of the boiling point of water (in degrees
Fahrenheit) and atmospheric pressure (in inches of mercury) taken at
seventeen sites in the Alps and in Scotland.  Forbes was interested in
predicting atmospheric pressure (and subsequently altitude) from the
boiling point of water.  Forbes' Theory suggested that over the range
of observed values, the logarithm of atmospheric pressure should be a
linear function of the boiling point.

See Weisberg (1985), "Applied Linear Regression," for more details.