This departed column may account for a fact which I discovered in another glaciere, and found to be of very common occurrence, viz., that in large stalagmites there is a considerable internal cavity, extending some feet up from the ground, and affording room even for a man to walk about inside the column.
When the melted snows of spring send down to the cave, through the fissures of the rock, an abundance of water at a very low temperature, and the cave itself is stored with the winter's cold, these thicker rings of ice catch first the descending water, and so a circular wall, naturally conical, is formed round the area of stones; the remaining water either running off through the interstices, or forming a floor of ice of less thickness, which yields to the next summer's drops.

In the course of time, this conical wall rises, narrowing always, till a dome-like roof is at length formed, and thenceforth the column is solid.

Of course, the interior cannot be wholly free from ice; and it will be seen from the account of one of these cavities, which I explored in the Schafloch, that they are decked with ice precisely as might be expected.[9] Another possible explanation of this curious and beautiful phenomenon will be given hereafter.[10] The temperature was half a degree lower than when there were three of us in the cave two days before.

I deposited one of Casella's registering thermometers, on wood, on a stone in that part of the floor which was free from ice, though there was ice all round it at some little distance.

The thermometer was well above the surface of the ice, and was protected from chance drops of water from the roof.
The next morning I started early from Arzier, having an afternoon journey in prospect to the neighbourhood of another glaciere, and was accompanied by Captain Douglas Smith, of the 4th Regiment.