This volcano was first observed by Captain Kater on Sunday the 4th of February, the moon being then two days old, with a Newtonian telescope of 6¼ inches aperture, and a power of 74. The position of the volcano is shown in an annexed drawing; its appearance was that of a small nebula, subtending an angle of 3 or 4 seconds, and its brightness very variable. It was again observed on the evenings of the 5th and 6th, but was then more faint, though occasionally exhibiting the appearance of a luminous point, like a star of the 6th or 7th magnitude. Captain Kater thinks that the distance of the volcano from the edge of the moon was about one tenth of her diameter; and the angle which it formed with a line joining the cusps on the last-mentioned evening, was about 50º. On the 7th it was scarcely visible, in consequence, probably, of the increased light of the moon.