23G ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



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 w T est. 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 2350 cubic feet, some of the stones be- 

 ing 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 be- 

 ing shallow, larger at the top than at the bottom, and very 

 j)roperly are called kettles, while others, as the one alluded 

 to, are deep, and could better be called wells. It is to be 

 observed that they are by no means necessarily found in 

 present river channels. They are most common in the neigh- 

 borhood of the great fiords, though they have been observed 

 too at a height of 1200 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 now ex- 

 ist 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 crevice 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 has been proposed. 



PROBABLE AGE OF THE CRYSTALLINE ROCKS OF THE SOUTH- 

 ERN APPALACHIANS. 



Professor Bradley, of Knoxville, Tennessee, has recently 

 published the results of his geological labors among the 



