In this speech Wilbur boldly declared that the best sets of figures obtainable regarding air pressure against airplane surfaces appeared to contain many serious errors. Orville, at the shop in Dayton, was a little alarmed about that part of the speech. What if something about their own work had been wrong and the figures compiled by various scientists should finally be proved correct? Certainly it was no small responsibility for anyone so little known as Wilbur or he to denounce publicly the work of eminent scientists, dignified by preservation in books long regarded as authoritative. It would be both presumptuous and risky to brand supposedly established facts as untrue unless the person doing so could be unassailably sure of his ground. In this cautious state of mind Orville rigged up a little wind-tunnel for the purpose of making a series of tests. This tunnel consisted simply of what appeared to be an old starch box, not more than eighteen inches long, that was lying in the shop. In it he placed a hastily constructed apparatus, a main part of which was simply a metal rod pivoted in the manner of a weather vane. Without attempting to give technical details of the method used, it may be said that a curved surface was balanced against a plane surface in an air current passing through the box. As Orville had provided the box with a glass top he could measure the angles to the wind at which the curved surface and the plane surface of equal area produced equal pressures. The experiments with this crude apparatus lasted only one day. They were conclusive enough so far as they went, indicating errors in published figures relating to air pressure on curved surfaces. But as Orville was later to learn, the published errors were greatest in regard to wing surfaces set at small angles, such as would be used in flying, and he had tested thus far only larger angles. With the tests thus incomplete, Orville and Wilbur decided, on the latter’s return from Chicago, that it might be prudent to stay on the safe side and omit from the published record of Wilbur’s speech the more severe part of his criticism of available figures. They would wait until further wind-tunnel experiments could give more detailed knowledge. Consequently, when Wilbur’s speech appeared in the December, 1901, issue of the _Journal of the Western Society of Engineers_, it was a bit less startling than the one he had actually delivered--though, even after the deletions, there still remained strong hints that accepted tables of figures might be wrong. And the record of the speech was treated as of great importance. It has probably been reprinted and quoted as often as any other article ever written on the subject of flying.