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ARTICLE VII.
COMPARISON OF THE PRINCIPLES.
To compare the two principles, viz. That of working with atmospheric steam to form a vacuum, which owing to its imperfection, seldom carries a load exceeding 12 pounds to the inch, with the new principle of working with strong elastic steam, equal to 120 pounds to the inch, which, shut off at 1/8 part of the stroke, (as No.1 in the table, article 6) carries a load equal to 48.7 pounds to the inch.
By article 3, every addition of a small quantity of fuel doubles the power and bulk of the steam; so that there remains no doubt but that doubling the fuel, that will produce atmospheric steam, will increase its elastic power to 120 pounds to the inch and move 8 times the the load an equal distance; producing 8 times the effect on that simple principle. But when we consider that we shut off at 1/8 part of the stroke, and are enabled to strike 8 times the number of strokes, carrying a load of 48.7 pounds, which, multiplied by 8 is equal to 389.6, the effect. Hence it appears that by doubling the fuel to obtain the strong steam, 32 times the effect is produced by the new principle.
But we rather believe that the steam will not bear to be shut off sooner than at 1/4 the stroke, which increases the average load to about 68 pounds to the inch, and enables us to strike only 4 times the number of strokes; then 4 multiplied by 68 is equal to 272, which, divided by 12, the load of the old principle, quotes 22.6 times the effect.
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Again, let us suppose a boiler with a furnace to consume 1 bushel of coals in an hour, with a cock opened so wide as just to let the steam (when its power is 15 pounds to the inch) escape freely into a vacuum. It has been ascertained that the velocity would be 1332 feet per second. Then suppose we increase the consumption to 2 bushels per hour, leaving the aperture the same; we believe the elastic power would be increased to 120 pounds to the inch, and the velocity of the steam would be as the square root of the pressure, viz. 3769 feet per second, we may say as quick as lightning, and the effects will be as the pressures multiplied into their velocities by the known laws of mechanics. Then, 15 multiplied by 1332 is equal to 19,980, the measure of the effect produced by 1 bushel of coals per hour, and 120 multiplied by 3769 is equal to 452,280 the measure of the effect produced by 2 bushels of coals per hour, 452,280 divided by 19,980 quotes 22.6, that is 22.6 times the effect produced by doubling the fuel.
We have not made experiments sufficiently accurate nor
discovered data from which we can calculate the different effects with accuracy,
but we know enough by experience with an engine in actual use, working on
the new principle in the most simple form, without a condenser, to be assured
that the gain of power and saving of fuel is very great; and may say with
safety, that doubling the fuel on this principle, produces at least 16 times
the power and effect.