Later we find:—
“... For the former case this is 0.0156 horse-power, and for the latter case approximately 0.0095 horse-power—that is, less power is required to maintain a horizontal velocity of seventeen metres per second than of fourteen, a conclusion which is in accordance with all the other observations and the general fact deducible from them, that it costs less power in this case to maintain a high speed than a low one—a conclusion, it need hardly be said, of the very highest importance, and which will receive later independent confirmation.”
“Of subordinate, but still of very great, interest is the fact that if a larger plane have the supporting properties of this model, or if we use a system of planes like the model, less than one-horse power is required both to support in the air a plane or system of planes weighing 100 lbs., and at the same time propel it horizontally at a velocity of nearly forty miles per hour.”
§ 234. Langley's Experiments. The “Component Pressure Recorder.”—This is by far the most important of the appliances originated by Prof. Langley for use in conjunction with the whirling table, and is one that should receive careful study from future experimenters. In construction, the component pressure recorder somewhat resembles the resultant pressure recorder already described, but instead of measuring the magnitude and direction of the total reaction by a symmetrical spring combination, the reaction is resolved into its horizontal and vertical components, which are separately recorded, the former directly on a chronograph cylinder forming part of the instrument, and the latter by the condition that the “soaring speed” is reached. It may be remarked that, whereas in the resultant pressure recorder the plane is counterpoised so as to be virtually weightless, in the present instrument the weight of the plane, loaded to whatever extent desired, is used as a measure of the vertical component.
The drawings of this instrument as figured in the Memoir are
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