[BARNES] ANCHOR-ICE FORMATION 77 



M. Fargeau, a distinguished professor of natural philosophy in 

 Strasbourgh, has made some observations on the Khine, which have been 

 communicated to the Academy, Notwithstanding what we have read, 

 they are very deserving of notice. 



On the 25th of January, 1829, at 7 o'clock a.m., the temperature 

 of the air, near the bridge at Kehl, was at 13°. 71 centigr. At the 

 eame moment, in that part of the Ehine which, owing to the situation 

 of its sand-banks, formed, on the French side, a sort of lake without cur- 

 rents, the water of which was at zero, but at the depth of 2/2 [?] metre 

 it was -f 4°.4. This place had only a few plates of ice near the banks. 



Beyond the banks of sand, in a little creek where the shallow 

 water was contiguous to a very rapid current, all the pebbles seemed 

 covered with a sort of transparent mass of from 3 to 4 centimetres in 

 thickness, and which, on examination, was found to consist of icy 

 spicula crossing each other in every directyjon. In this creek the ther- 

 mometer stood at zero cent, both at the surface and at the bottom of 

 the water. It was the same even in the most rapid part of the cur- 

 rent. There was also seen, either in the channel of the Ehine, or on 

 some pieces of wood on the side opposite to the current, at a depth 

 of 2 metres, large masses of spongy ice, into which the pole of a water- 

 man entered with ease. This ice, on being borne to the surface of 

 the water, wasi found closely to resemble the innumerable flakes which 

 were at that time floating on the surface. M. Fargeau states, that 

 he saw ice on many occasions with his oivn eyes, in the greater Rhine, 

 separate from the bottom, and rise to the surface. 



M. Fargeau has added an important observation to his own 

 remarks, which was communicated to him, and from whence the result 

 is derived, that the nature of the bed of the river has the same influ- 

 ence on the phenomena of congelation in small and in large currents 

 of water. In the Vosges, a superintendent of forges, informed him, 

 that, to prevent the formation of ice at the bottom of the rivulet which 

 supplied his establishment, he was obliged once a year to remove the 

 stones and other foreign bodies with which the channel became acci- 

 dentally covered. 



In the beginning of February, 1830, M. Duhamel, on breaking the 

 ice which covered the surface of the Seine, a short way below the 

 bridge at Grenelle, about 10 feet from the banks, found a layer of 

 continuous ice 4 centimetres thick. He even procured many frag- 

 ments. At this spot the water was upwards of one yard deep. Alt 

 every depth the thermometer stood at zero centigr. The current was 

 tolerably rapid. 



The experiment of M. Duhamel had this defect, like that of Hales 

 formerly mentioned, of having been made too close to the bank. I 



