The History: Octave Chanute replied to Wilbur's letter of August 2nd. He included the gliding results from his 1896 double-decked machine.

Date	Operator	Distance [feet]	Time [seconds]	Descent Angle	Height Fallen [feet]	Wind Miles Per Hour
Sept. 4	Herring	239	....	11°	46.3	15
Sept. 11	Avery	199	8	7.5°	34.6	31
Sept. 11	Avery	256	10.2	8°	35.5	31
Sept. 12	Herring	359	14	10°	62.1	25

Chanute described his method of wind measurement during the testing of his 1896 double-decked machine. Wind speed was recorded with an anemometer at the top of the hill. This was done once or twice [but not everytime]. In 1902, the anemometer had been calibrated and it was determined that the wind speed should be multiplied by 0.81 to obtain the true wind velocity.

Quotation from the book The Papers of Wilbur and Orville Wright, Volume 1 by M. McFarland.