[BARNES] ANCHOR-ICE FORMATION 71 



On the Ground-Ice or the Pieces of Floating Ice observed in 

 elvers during winter. 



By M. Arago. 



From Edinburgh New Philosophical Journal, Vol. 15, p. 123 (1833). 



The severe winter of 1839-30 has attracted the attention of natural 

 philosophers to the phenomena of congelation in running waters. They 

 have examined how, and in what manner, immense quantities of ice 

 are formed which some rivers carry down to the sea, and which, on 

 being piled up against the arches of a bridge, often cause fatal acci- 

 dents. I confess that, in a theoretical point of view, the question 

 does not yet seem, in my opinion, to be exhausted. Is it not a strong 

 reason, then, for my presenting as complete an analysis as possible 

 of the observations to which it has given rise? For want of a definite 

 solution of so curious a problem, I shall at least have placed before 

 the eyes of meteorologists a complete tabular view of all the data with 

 which it is indispensable that the explanation shall agree. 



Every one knows that in a lake, a pond, in every sheet of stagnant 

 water, congelation proceeds from the exterior to the interior. It is 

 the upper part of the surface of the water which is primarily affected. 

 The thickness of the ice afterwards increases in proceeding from above 

 downwards. 



Is this the case with running waters? N"atural philosophers are 

 of this opinion. On the other hand, millers, fishermen, and watermen, 

 maintain that the masses of ice with which rivers are crowded in the 

 winter season, proceed from the bottom. They pretend that they have 

 seen them rise, and have often borne them up with their hooks. They 

 say. in order to strengthen their opinion, that the inferior surfaces 

 of large flakes of ice are impregnated with mud; that it is encrusted 

 with gravel; that, in short, it bears the most unequivocal marks of 

 the ground on which it rested; that, in Germany, the sailors have a 

 peculiar and characteristic term to designate floating ice which they 

 call grundeis, i.e., ground-ice. Such arguments make little impression 

 on prejudiced minds. It would require nothing less than the evidence 

 of many experienced philosophers to cause a belief in the reality of a 

 phenomenon which seems directly opposed to the laws of the propaga- 

 tion of heat. But it is so. This evidence is not awanting; and if 

 the phenomenon of ice in the bottom of water has only appeared 

 recently as an established fact in treatises on physics and meteorolog}', 

 the reason is, because their authors generally copy from each other, 



