APRIL 5, 1901. ] 
but 7 kilograms per horse-power-hour at its 
rating, a trifle more at 342 delivered horse- 
power, and, a most remarkable achievement, at 
one-tenth its rated power only increases the 
consumption of steam to 9.74 kgs. This is 
better than any record yet reported for the 
reciprocating engine in maintenance of effi- 
ciency with diminishing delivery. The steam- 
pressure was about 8.5 atmospheres. Super- 
heating gave about ten percent. gain. The 
speed of the machine was about 10,000 revolu- 
tions a minute. A condenser was employed. 
The Engineer-in-Chief of the U. S. Navy, 
Admiral Melville, reports in his annual mes- 
sage to the Department a remarkable set of 
data from the trial of the water-tube boilers 
of the U. S. S. Cincinnati. Steam was raised 
from cold water to a pressure of 215 pounds in 
12 minutes, 40 seconds and without injury. 
The old shell-boiler would have needed several 
hours for getting up steam and, if forced, 
would have been expected to develop leaky 
tubes in all directions. After steam was up, 
the series of trials reported on was made, with 
forced draught, fuel being burned at rates 
ranging between 20 pounds, as a minimum, to 
above 50 pounds, per square foot of grate area, 
and with resulting evaporation of water of 
from nine pounds per pound of fuel, at the 
minimum, to 8.6 at the maximum rate of com- 
bustion. This is the equivalent of from 12.19 
to 11.43, ‘from and at’ 212° F., per pound of 
combustible portion of the fuel, an efficiency 
of boiler of from 85 to 90 per cent. The coal 
used was of the Pocahontas variety, which con- 
tains ordinarily but two or three per cent. of 
ash. Here the ash and refuse in unburned 
coal and clinker amounted to about ten per 
cent. This is the most remarkable performance 
of which we have record. The evaporation is 
excellent at the lowest rate of combustion and 
wonderfully well sustained through the higher 
ranges. It probably constitutes a world’s rec- 
ord to date. 
Gas and oil and petroleum-vapor engines are 
also coming to the fore in a remarkable way 
and the beginning of the twentieth century 
already commences to show the quality of the 
new era in these directions Mr. H. A. Marshall 
hasrecently presented a paper to the British 
SCIENCE. 
5D3 
Institution of Mechanical Engineers, now just 
published, in which he gives the outcome of 
investigations of the efficiencies of the gas- 
engines employing ‘ power-gas’ of the Mond 
variety, differing from the well-known Dow- 
son gas in the fact that it is made from 
bituminous ‘slack,’ instead of from anthra 
cite. It requires the use of enormous quanti 
ties of steam—250 per cent. of the weight of the 
fuel—and makes a very lean gas; but it em- 
ploys so cheap a grade of fuel as to furnish 
the unit of heat at an unprecedentedly low 
cost. It makes 150,000 cubic feet of gas per 
ton and this yields 2,000 horse-power-hours 
in large gas-engines of good construction. A 
by-product, ammonium sulphate, more than 
recoups the original cost of the fuel, with the 
English coals used. The outcome of this im- 
provement and of the adoption of the gas- 
engine in large sizes for extensive work is 
that, whereas the cost of fuel for the ideal 
steam-engine of modern practice should not 
exceed about a half-cent, the real engine de- 
mands,as a minimum, one cent, and the average 
engine of the large British stations one and a 
half-cent, or more; while the gas-engine has 
come down to a considerably lower cost than 
the minimum just given. The figures for heat- 
units demanded are reported as about 25,000 
B. T. U. per horse-power-hour for the best 
steam-engine and but 11,500 for the gas-engine, 
under best conditions and continuously work- 
ing. The real comparison is necessarily that 
of costs of production of the unit of power and 
it is this relation which will ultimately deter- 
mine the supremacy of one of the competing 
heat-engines. 
Gas-engines are now built in large powers— 
1,500 H. P., and larger powers can be readily 
supplied if called for—and are found to involve 
less practical difficulty on the large than on 
the small scale. They are now durable, regu- 
late well and are economical in use of exceed- 
ingly cheap fuels. The results obtained at 
Winnington, as reported by Marshall, are, in 
fact, not only better, thermodynamically, than 
those given by any existing steam-engine, but 
are even better than even the ideals of the case 
brought into the comparison; all of which are 
engines in use in English power and lighting 
