We were unable to measure the whole length of the wall in the lower cave, from the large number of blocks of stone which had fallen at one end, and lay against its face.

Probably, from the nature of the case, it was not so long as the 72 feet of wall above; but we measured 50 feet, and could see it still passing on to the right hand as we faced it.

In trying to penetrate farther along the face, I found a wing of the brown fly we had seen in considerable abundance on the ice in La Genolliere, frozen into the remains of a column.
There was so very much to be observed on all sides, and the measurements took up so much time, owing to the peculiar difficulties which attended them, that I did not examine with sufficient care the curious floor of ice through which we cut our way to the lower cavern.

Neither did I notice the roof of the cavern thus reached, which may be very different from the shape of the upper surface of the floor composing it.

If the ice-wall goes straight up, and the roof is formed of the ice-floor alone, then it is a very remarkable feature indeed.