Rensselaer Union, Volume 7, Number 32, Rensselaer, Jasper County, 29 April 1875 — Giant Kettles. [ARTICLE]

Giant Kettles.

It is not always that geological investigations have as their object phenomena Which are of general interest and with which all are more or less familiar. This is certainly the case,' however, with the study of tne “ giant kettles” in the neighborhood of Christiania, Norway, which has been lately carried on by Prof. Kjerulf and some of his students. There is hardly any running stream in our country of any considerable size which does not give proof of the power of water and stones in motion in what are popularly called “pot-lioles.” An eddy in the stream where the current is strong sets a few pebbles in revolution. These commence a depression, into which larger stones fall, and the grinding is continued until a cavity has been produced perhaps several feet in depth, and almost perfectly round. These are often to be observed, not only in stream beds, but. also in rocks on the sea shore, where the rush of the. tide must supply the motive force. The famous “ giant kettles” of Norway are simply “ pot-holes” on a larger scale and produced in, former times under somewhat different conditions than we have at present. The superstition of the people represents mem as having been made by giants. In some places, where the form is oblong and irregular, fancy has seen in them the footprints of these monsters, while in one place, where the road goes directly through a very large kettle, the saying is that there St. Olaf turned liis horse around. On the west coast of Norway another name is used, and they are spoken of as giants’ chairs. The description of one of these kettles examined by Prof. Kjerulf will give some idea as to their size and general character. At the surface it had a diameter of about eight feet, being slightly elliptical in form. It widened considerably,ip the descent, and then contracted again at the bottom. It is interesting to note' that the walls were distinctly worked out jn a spiral, which could be traced from top to bottom. In the case of some other kettles examined the spiral was so perfect that the cavity could be compared to the impression of a gigantic snail. The total depth of the kettle in question from the highest point of the margin was forty-four feet, the axis inclining somewhat toward the west. It was filled, as is always -the case, with gravel and broken rock, though toward the bottom numerous so-called grinding-stones were found, some of them 300 pounds in weight, and all smooth and elliptical in shape. It was through their revolution that the excavation had been made. It required three men working for fifty days to clear this giant kettle of its contents, and the whole amount taken out was estimated at 2,350 cubic feet, some of the stones being so large that they had to be mined before they could be hoisted out. The kettles in general present much the same features as the one which has been just described, though there is a great variation in ratio of width to depth, many of them being shallow, larger at the top than at the bottom, and very properly are called kettles, while others, as the one alluded to, are deep, and could better he called wells. It is to be observed that they are found by no means necessarily in present river channels. They are most common in the neighborhood of the great fiords, though they have been observed too at a height of 1,200 feet above the sea. In regard to their origin, the best authorities refer it to the time when the land was covered by enormous glaciers, such as exist at the present time in the upper part of Greenland. The melting of the ice on the surface of glaciers gives rise to. considerable rivers, and as these find some crevasse in the ice they descend with violence, and it is conceivable that such a stream striking the bed rock below might be the means, with the masses of rock they would put in motion, of producing the enormous cavities which are now observed. This theory as carried out by its supporters meets with some difficulties, but seems to be the best which lias been proposed.