56 Natural-Historical Collections. 



At this period, M. Marian, professor of natural philosophy at Bale, wrote 9 

 memoir, in which he contended that the opinion of the vulgar, on the formation 

 of ice at the bottom of rivers, is founded on satisfactory evidence. Convinced by 

 the different statements in favour of the reality of this phenomenon, he was alrea- 

 dy prepared to admit its existence, when in 1 824 he observed it himself in a ca- 

 nal whose water was so transparent that he could distinctly see the bottom at a 

 depth of three feet. The bed of the canal, at the place observed, was formed of 

 rolled flints. But wherever there could be perceived at the bottom of the water 

 a projection in the deep parts as well as in the more shallow places, a fasciculus 

 of pieces of ice was found, at a distance resembling a quantity of woolly flakes. 



I\I. Marian added to this observation many facts equally conclusive. In IU06, 

 it was stated by a creditable observer, that some chains of six feet in length, 

 which had been a long time lost under water, on being raised to the surface, 

 were found entirely covered with a thick coat of ice. The same person related 

 that an anchor, after being an hour in the water, had also been drawn out covered 

 with ice. 



New and more detailed observations on this subject, were made in the winters 

 of 1827 and 1829, by another savant, M. Hugi, president of the natural history 

 society of Geneva. During many successive hours, he observed ice rise in great 

 quantities from the bottom of the Aar at Solerne. But M. Hugi did not confine 

 himself to the mere remark that ice rose from the bottom of the river. He exa- 

 mined its structure minutely in comparison with that of the ice found on the sur- 

 face, and has noticed remarkable differences between them. 



A professor of natural philosophy at Strasbourg has also seen ice adhering to 

 the bottom of one of the canals formed by the Rhine near this place, and has 

 published his observations in a thesis this year. 



Finally, M. Duhamel, satisfied of the reality of the fact, as well by the preced- 

 ing observations as by many others of a similar kind which M. Navier had com- 

 municated to him, and by others for which he was indebted to M. Vauvilliers, 

 chief engineer of roads and bridges, was curious to have personal assurance, and 

 in February last, he remained for same days on the banks of the Seine, near the 

 bridge of Crenelle, and there he observed at eight or ten feet from the brink, in 

 a place where the current was very rapid, that the bottom of the river was coated 

 with a layer of ice firmly adhering. He however detached with a pole some 

 pieces whose thickness was fifteen or sixteen lines. The temperature of the wa- 

 ter was at zero at the surface and at the bottom. 



M. Duhamel, in a letter addressed to M. Navier, which was read before the 

 Academy of Sciences of Paris on the 8th February last, explains how, according 

 to his opinion, we must account for the formation of ice at the bottom of running 

 water. In stagnant water, whose current is insensible, it has been remarked, he 

 says, that the temperature of the bottom continues above zero, even when the 

 surface is frozen. This phenomenon is explained by the known law of the spe- 

 cific gravity which water preserves at different degrees of temperature, — a law, by 

 virtue of which the water acquires, between three and four degrees above solidifi- 

 cation, a maximum of density which must necessarily cause it to fall to the bot- 

 tom, and to remain there at this temperature. Thus we never find ice at the 

 bottom of such a collection of water. But in a rapid current the unequal mo- 

 tion of the molecules, at different depths and at different distances from the banks, 

 must produce a mixture which will bring all parts to the same temperature. For 

 the banks and the bottom are in the most favourable conditions for the formation 

 of ice, and it would be strange if it did not take place when the mass is down at 

 sero. The bottom must furnish a much greater quantity than the margin, and 

 it would even appear that the floating ice comes almost entirely from the bottom, 

 since that which is formed at the sides generally remains attached. 



Since the relation of M. Duhamel's observations on the formation of ice at the 

 bottom of the Seine, a letter from Colonel Raucourt has been read before the 

 Academy, (sitting of 15th Feb. last,) containing several observations, at different 

 periods, on the temperature of the Neva, and on the formation of ice at the bot- 

 tom of this river. 



