The Locomotive - Lighthouse Survival Blog

60 THE LOCOMOTIVE [April,
estimates of the position of the absolute zero being —455.2° and 447.7°. These
results are shown plotted in the diagram, the separate experiments for carbonic acid gas
being represented by dots, enclosed within small circles. The horizontal distance of
each of these dots from the vertical line on the left represents the initial pressure of the
gas when the corresponding experiment was made ; and the heights of the respective
dots represent the corresponding estimates of the position of the absolute zero. The
experimental data are evidently not perfect; but if we draw a straight line as nearly as
-460--
-450'—
-440-
-430
INITIAL PRESSURE OF THE GRS. IN ATMOSPHERES
possible through the dots and prolong it until it cuts the vertical line, we find that it
does so at a point corresponding to —461.1°. We therefore conclude that if we had
worked with carbonic acid gas of a density so low that its pressure at 32° would be
practically nothing, we should have concluded that the absolute zero is 461.1° below the
ordinary zero. In other words, this is the zero point of the perfect gas thermometer as
indicated by our experiments on carbonic acid gas.
Regnault also made a similar series of experiments on air, which we can treat in
precisely the same way. It will not be necessary to give the numerical data, but the
points that are obtained by proceeding in the same manner as before are indicated in the
diagram by crosses; and if we draw a straight line through these crosses, as nearly as
we can, we find that this line cuts the vertical line at the same point as before, as it
ought to, if our reasoning is correct. If we had a sufficient number of experiments of