Page:Passages from the Life of a Philosopher.djvu/235

Rh these ditches with red-hot bottoms which, in the darkness of the night, had presented the singular spectacle I described as having witnessed on the evening before.

At one extremity of this oval plain there was a small cone, from which the eruptions before described appeared to issue.

My first step, after examining the few instruments I had brought with me, was to select a spot upon which to measure a base for ascertaining the depth of the crater from its upper edge.

Having decided upon my base line, I took with my sextant the angle of elevation of the rim of the crater above a remarkable spot on a level with my eye. Then fixing my walking-stick into a little crack in the scoria, I proceeded to measure with a tape a base line of 340 feet. Arrived at this point, I again took the angle of elevation of the same part of the rim from the same remarkable spot on a level with the eye. Then, by way of verification, I remeasured my base line and found it only differed from the former measure by somewhat less than one foot. But my walking-stick, which had not penetrated the crack more than a few inches, was actually in flames.

Having noted down these facts, including the state of the thermometer and barometer, in my pocket-book, I took first a survey and then a tour about my fiery domain. I afterwards found, from the result of this measurement, that our base line was 570 feet below one of the lowest points of the edge of the crater. Having collected a few mineral specimens, I applied myself to observe and register the eruptions of the little embryo volcano at the further extremity of the elliptical plain.

These periodical eruptions interested me very much. I proceeded to observe and register them, and found they occurred