84 ROYAL SOCIETY OF CANADA 



by the name of glace dc fond; and in the soutli of Scotland it is called 

 lappered ice, an epithet which tlie common people apply to the natural 

 congelation of milk. I am happy, however, that the phenomenon has 

 now attracted the attention of some eminent philosophers, particularly 

 of the celebrated Arago in France, who has been at great pains in 

 collecting a variety .of facts, and has proposed a theory for the explan- 

 ation of the appearance, which I shall shew to be utterly inadequate 

 for the purpose; and which, with the modesty that characterizes genuine 

 philosophy, he admits does not thoroughly satisfy himself. 



I beg leave to call the attention of the meeting, for a moment, 

 to the phenomenon itself. /Every inhabitant of Perth who has wit- 

 nessed the setting in of a severe frost, must have observed that before 

 the true ice. as I may call it, has made much progress in advancing 

 from the sides to the centre of the river, nearly the whole body of 

 the stream above the bridge is occupied by large irregular masses of 

 floating ice of very considerable thickness, far beyond any thing that 

 could be effected l)y the natural operation of the frost in surface freez- 

 ings. I believe it has seldom occurred to any observer to inquire how 

 these masses of amorphous ice were formed; they all come down the 

 river from a great distance; and being stopped, at last, by the flow 

 of the tide, and. clo»sely compacted together, they are agglutinated by 

 the frost, and present great obstacles to navigation. Now these masses 

 are precisely the ice in question; they are formed in the most rugged 

 currents, adhering to the projecting rocks and rough inequalities at 

 the bottom, and increasing upwards, till their bulk and smaller specific 

 gravity as compared with water, enable the stream to tear them from 

 their fastenings, and hurry them down th.e river. 



I shall mention a few of the facts which M. Arago has collected 

 on this subject, and it is curious enough to observe from this statement 

 that, what is perfectly well known to every peasant, is still called in 

 question by the majority of the natural philosophers of France; they 

 deny the existence of ground-ice. 



M. Beaun, in 1788, Avrote several dissertations chiefly to establish 

 the existence of ground-ice, from observations made by himself and 

 by the fishermen on the Elbe. Ke informs us, that the latter declared 

 that the baskets which they let down into the river, for the purpose 

 of catching eels, were often when brought to the surface, incrusted 

 with ice; that the anchors used for mooring their boats when lost 

 during the summer, again appeared in the following winter, being 

 raised by the ascending force of the ice at the bottom, with which 

 they had been covered to snch an extent as to render them buoyant; 

 and that this ground-ice often raised up the large stones to which the 



