The arch of entrance was so low, that the top was about on a level with my waist; so that our faces and the upper parts of our bodies were not exposed to the current, and the strangeness of the effect was thus considerably increased.  As a matter of curiosity, we lighted a bougie, and placed it on the edge of the snow, at the top of the slope of 3 or 4 feet which led down the surface of the ice, and then stood to watch the effect of the current on the flame.  The experiment proved that the currents alternated, and, as I fancied, regularly; and in order to determine, if possible, the law of this alternation, I observed with my watch the exact duration of each current.  For twenty-two seconds the flame of the bougie was blown away from the entrance, so strongly as to assume a horizontal position, and almost to leave the wick:  then the current ceased, and the flame rose with a stately air to a vertical position, moving down again steadily till it became once more horizontal, but now pointing in towards the cave.  This change occupied in all four seconds; and the current inwards lasted—­like the outward current—­twenty-two seconds, and then the whole phenomenon was repeated.  The currents kept such good time, that when I stood beyond their reach, and turned my back, I was enabled to announce each change with perfect precision.  On one occasion, the flame performed its semicircle in a horizontal instead of a vertical plane, moving round the wick in the shape of a pea-flower.  The day was very still, so that no external winds could have anything to do with this singular alternation; and, indeed, the pit was so completely sheltered by its shape, that a storm might have raged outside without producing any perceptible effect below.  It would be difficult to explain the regularity of these opposite currents, but it is not so difficult to see that some such oscillation might be expected.  It will be better, however, to defer any suggestions on this point till the glaciere has been more fully described.

[Illustration:  GROUND PLAN OF THE GLACIERE OF MONTHEZY.  Note:  The candle stood at this point.]

We passed down at length through the low archway, and stood on the floor of ice.  As our eyes became accustomed to the darkness, we saw that an indistinct light streamed into the cave from some low point at a considerable distance, apparently on a level with the floor; and this we afterwards found to be the bottom of the larger of the two pits we had already fathomed, the pit A of the diagram; and we eventually discovered a similar but much smaller communication with the bottom of the pit B. In each of these pits there was a considerable pyramid of snow, whose base was on a level with the floor of the glaciere:  the connecting archway in the case of the pit A was 3 or 4 feet high, allowing us to pass into the pit and round the pyramid with perfect ease, while that leading to the pit B was less than a foot high, so that no passage could be forced.