home. The lower numbered frame showed a mountain whose top was very nearly centered within the frame. The foreground detail was in sharp focus indicating that either a fairly high shutter speed had been used or the camera had been stabilized or both. Figure 1 is an enlargement of the full negative reproduced as a positive print. A sharply focused disc-like object is seen above and to the right of the mountain top. The tip of the mountain was located close to the geometric center of the 35 mm frame. This tends to support the statement made by the photographer that she was intent upon photographing the mountains and never saw the aerial object. The presence of a cloud directly illuminated by sunlight through extremely clear air provides a useful upper exposure limit in later densitometry measurements. Dark shadows seen within a stand of trees in the left foreground provides a lower end to the exposure. Thus, a maximum of 12,500 ft-L is assumed for the luminance of the cloud and approximately one ft-L for the shadow area. The atmospheric clarity makes it almost impossible to judge separation distance between the camera and object by means of an extinction coefficient calculation.

The negative measured 36 x 24 mm. A photographic enlargement of the disc image provided for linear measurements. Its major axis on this print was 5.70 cm while its minor axis was 1.60 cm for a width/height ratio of 3.56. The width of the "dome" protruding from the upper surface was 1.3 cm and

Fig. 1. Photograph of mountain and disc.