undetermined was the temperature of the furnace, an omission due to
the want of a trustworthy pyrometer, a want which has not been
satisfied to this day.[2]

[Footnote 2: In the fifty-second volume of the _Proceedings_
(1887-78), page 154, will be found a remarkable experiment on the
evaporative power of a vertical boiler with internal circulating
pipes. The experiment was conducted by Sir Frederick Bramwell and
Dr. Russell, and is remarkable in this respect, that the quantity
of air admitted to the fuel, the loss by convection and
radiation, and the composition of the smoke were determined. The
facts observed were as follows:

Steam pressure 53 lb................................... = 300.6° F.
lb.
Fuel--Water in coke and wood........................... 26.08
Ash.............................................. 10.53
Hydrogen, oxygen, nitrogen, and sulphur.......... 7.18
------
Total non-combustible..................... 43.79
Carbon, being useful combustible................. 194.46
------
Total fuel................................ 238.25

Air per pound of carbon................................ 17-1/8 lb.
Time of experiment..................................... 4 h. 12 min.
Water evaporated from 60° into steam at 53 lb. pressure 1,620 lb.
Heat lost by radiation and convection.................. 70,430 units.
Mean temperature of chimney............................ 700° F.
" " " air................................ 70° F.