78 ROYAL SOCIETY OF CANADA 



could not, however, omit quoting it, as I am not aware of any observ- 

 ation to be found elsewhere by a man of science respecting the con- 

 gelation at the bottom of the Seine. 



It has been mentioned already, tliat natural philosophers did not 

 believe in the formation of floating ice at the bottom of water; they 

 ought, therefore, not to expect that any thing very important will 

 he found in the sketch I am about to present of the theoretical specu- 

 lations to which this theory has given rise. 



Sailors for the most part believe that the flakes of ice are formed 

 at night on the bottom of rivers, by the action of the moon, and that 

 it is the sun which attracts them to the surface on the following day. 

 Popular prejudices are generally grounded on some imperfect observ- 

 ation. By recollecting what we said concerning the red moon we shall 

 (easily discover how the strange notion of which I have spoken arose. 



The theory of the sailors was not succeeded by an explication in 

 any degree better. It was said that heat arises from the rapid move- 

 ment of the parts of bodies. The running water flows less rapidly 

 at the bottom than at the top, the maximum of temperature is, of 

 course, found at the surface; it is at the bottom, where there is the 

 least agitation, that the congelation ought to begin. To complete this 

 theory, the ascension of the flakes of ice was attributed to the elas- 

 ticity which the air dissolved in the water resumes when it disengages 

 itself during the process of congelation, and to the formation, in the 

 midst of the icy mass, of bulrbles of considerable size. 



In 1742, when this strange theory saw the light (Observations sur 

 les Ecrits modernes, t. xxxi.), the thermometer was in the hand of 

 every person, and, of course, it could have been easily ascertained that, 

 during a hard frost, river water is in general colder at the surface 

 than at the bottom. But, as Montaigne says, even in the facts which 

 are laid before them, men willingly amuse themselves in seeking for 

 reasons rather than truth ; they abandon things and fly to causes. 



To reconcile the theoretical objection which Xollet has made to 

 the popular opinion respecting ice at the bottom of water, with the 

 observations which incontestibly establish that the greater part of the 

 flakes which have been broken up have been immersed for a longer or 

 shorter period, and that their inferior surface rests on a muddy bottom, 

 it has been thought that the origin will be found in the small streams 

 which run into large rivers. There, it is said, the water being shallow, 

 the ice should soon find itself in contact with the ground or mud 

 with which the bed is covered. As to the flakes of ice which rise 

 beneath the water, which sailors bring up with their hooks from a 

 depth of some "?eet, their existence is explained by remarking that, 

 after a sharp frost followed by the commencement of a thaw, there 



