of the planes) was sufficient to prevent any sensible interference between the two pairs, so that each would carry the same load as if the other were absent. Trials with the planes two inches apart showed a falling-off of about 15 per cent, of the total load.
Fig. 101.
It would appear that when the inclination of the plane exceeds five or six degrees, some interference is felt even at four inches separation. This is doubtless to be attributed to some change in the type of fluid motion, such as that suggested in Fig. 98; on the other hand, no increase in the velocity, and therefore diminution of the angle, is found to prevent the interference taking place when the distance apart is reduced to two inches.
Referring to these experiments Langley says:—“The most general, and perhaps the most important, conclusion to be drawn from them, appears to be that the air is sensibly disturbed under the advancing plane for only a very slight depth; so that for the
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