mercurial thermometers registering 600° Fahr., except those near the
mouthpiece, which were taken by a Siemens water pyrometer. Every care
was exercised to insure accuracy; and the instruments were carefully
adjusted. At a distance of 18 inches from the mouthpiece, the
temperatures varied from an average of 890°, shortly after the retort
was charged, to 518° at the end of the charge; at 12 feet distant from
the mouthpiece, the corresponding temperature was 444°, falling to
167° at the end of the charge; and at 22 feet, the average temperature
varied from 246° at the commencement to 144° at the end of the charge.
These are the averages of a number of experiments. In some instances
they were considerably above these averages--temperatures over 900°
being frequently obtained. This is about the temperature of a low red
heat, and is much higher than any I have seen recorded. When the gas
was allowed to issue from a hole in the ascension pipe, 1¼ inches in
diameter, 18 inches above the mouthpiece, a strip of lead held about
an inch from the orifice was freely melted.

In the settings on which these experiments were made, the middle
ascension pipe takes the gas from the two central retorts; and it is
of interest to note that in this pipe the temperature of the gas 18
inches from the upper retort was found to be 1014° Fahr., and at the
point where it entered the hydraulic main it was 440° Fahr. Zinc was
freely melted by the gas issuing from a hole 18 inches from the
mouthpiece. The temperatures always fall toward the end of the charge;
the fall of temperature in the ascension pipe being a good indication
that the charge is worked off. They increase with the heat of the
retort and with the weight of the charge.

Experiments were also made to ascertain the temperature of the gas in
the retort; and for this purpose one of Murrie's pyrometers was used,