A distinct stable auroral red arc was observed on the night of September 25/26, 1978, with a multicolor meridian scanning photometer and a 6-inch high-resolution Fabry-Perot interferometer. The results obtained include the following: (1) the growth rate on intensity of the arc was very rapid, and the time constant measured as 20 min; (2) the average southward drift velocity was rather fast, v~240 km/h or dl/dt~-0.28 per hour; and (3) the temperatures within the arc showed an increase of about 200¿K at round 2.7 hours after the appearance of the arc, while no other enhancement of the temperature was observed during the observation period.