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Show 10 which was not snow covered. Anemometers were mounted with cups 43 cm. above ground level at 4.5 m upwind, and at 4.5 and 9 m downwind from the center of the jet roof. Wind speed measurements were made for jet roof inclination angles from 10° through 80° from the horizontal. The results of these measurements are given in Table 1. As can be seen, downwind acceleration of the air is maximized with inclination angles between ' 0 and 20 . Although the measurements indicate a decrease in wind speed for roof angles greater than 30°, in actual use angles greater than 30 can be used on ridges which have correspondingly steep lee slopes. In order to reconcile the apparent contradictions of the effectiveness of steep roof angles with the reduced downwind velocity, a short series of wind tunnel experiments were made using a laboratory scale of the jet roof. The model used was a 1: 48 scale of the field jet roof. Measurements of the percent increase or decrease in the wind speed downwind of the laboratory model jet roof were made at approach speeds of approximately 7, 6, 3- 8, and 1.9 m/ sec. Changes in mean wind speed at the approach position did not produce a consistent downwind effect beyond the jet roof although there was some variation in the relative changes. The results of the model study given in Table 2 agree roughly with the results which were obtained in the full scale tests for the same relative positions of the anemometers. In addition to comparing the wind speed in the laboratory model with wind speed in field tests ( at the same relative positions), measurements were made at several other positions downwind of the laboratory model jet roof. Specifically, the speed at the lee edge of the model roof was found to be increased by approximately 10, 15, |