In endeavouring to understand the phenomena of volcanoes it is very desirable that the student should understand what goes on in a normal eruption. The writer may, therefore, be warranted in describing some observations which he had an opportunity to make at an eruption of Vesuvius in 1883, when it was possible to behold far more than can ordinarily be discerned in such outbreaks--in fact, the opportunity of a like nature has probably not been enjoyed by any other person interested in volcanic action. In the winter of 1882-'83 Vesuvius was subjected to a succession of slight outbreaks. At the time of the observations about to be noted the crater had been reduced to a cup about three hundred feet in diameter and about a hundred feet deep. The vertical shaft at the bottom, through which the outbursts were taking place, was about a hundred feet across. Taking advantage of a heavy gale from the northwest, it was practicable, notwithstanding the explosions, to climb to the edge of the crater wall. Looking down into the throat of the volcano, although the pit was full of whirling vapours and the heat was so great that the protection of a mask was necessary, it was possible to see something of what was going on at the moment of an explosion. The pipe of the volcano was full of white-hot lava. Even in a day of sunshine, which was only partly obscured by the vapours which hung about the opening, the heat of the lava made it very brilliant. This mass of fluid rock was in continuous motion, swaying violently up and down the tube. From four to six times a minute, at the moment of its upswaying, it would burst as by the explosion of a gigantic bubble. The upper portion of the mass was blown upward in fragments, the discharge being like that of shot from a fowling piece; the fragments, varying in size from small, shotlike bits to masses larger than a man's head, were shot up sometimes to the height of fifteen hundred feet above the point of ejection. The wind, blowing at the rate of about forty miles an hour, drove the falling bits of rock to the leeward, so that there was no considerable danger to be apprehended from them. Some seconds after the explosion they could be heard rattling down on the farther slope of the cone. Observations on the interval between the discharge and the fall of the fragments made it easy to compute the height to which they were thrown.