90 ROYAL SOCIETY OF CANADA 



or angles, or points, iDroraisciionsly. Botli the lirmness of the adhesion 

 and the dimensions of the interstices (the latter filled with water, and 

 their volume easily estimated by the quantity of it which is discharged 

 when the ice is lifted out of the stream), are, however, greatly modified 

 by the intensity and continuance of the previous cold. When the 

 ice begins first to form on tlie bottoms of the streams, it presents a 

 rudely symmetrical appearance, which, for illustration, may be com- 

 pared to little hearts of cauliflowers, fixed on the bottom, having a 

 similar uniform circular outline and protuberance in the centre, with 

 coral-like projections. These pieces have a shining silvery aspect; 

 they are dispersed, at first irregularly, in small numbers, but increase 

 both in size and numbers, till the whole bottom is covered, and, if 

 the frost continues severe, grow in height, but in a very irregular man- 

 ner, so as to obliterate the earlier somewhat symmetrical shapes, till 

 the streams are raised high above their former levels, and frequently 

 made to overflow their banks. 



And here I take the opportunity to notice the incorrectness of an 

 observation of Desmarest, quoted by M. Arago, and which, as M. Arago 

 observes, no one has corroborated, " that it was from the lower parts, 

 which touched the bottom, that the fl.akes of ice successively increased." 

 On the contrary, the forms of the surface of the earlier masses are 

 continually obscured, in succession, by new ice added to the top. 



This congealed mass being thus very different in appearance and 

 consistence from the sheets or plates generally known by the name of 

 ice, it were no doubt well that, like the Germans who, M. Arago informs 

 UP, name it grundeis, we too designated it by another name, to prevent 

 confusion or misapprehension when we refer to it. The inhaliitants 

 of this part of the country will furnish us with a better one than 

 even that of the Germans. In a district where it occurs almost every 

 winter, and often repeatedly during the season, and where many of 

 the rivers are crossed by means of fords, its existence influences too 

 much their economical arrangements not to excite their particular 

 attention, especially as many horses refuse to enter any stream even 

 slightly impeded by it, being greatly alarmed by the pieces which break 

 and float up from the bottom by the action of their feet. A body 

 with which all are so well acquainted is known by an appropriate name. 

 They call it ground-gru ; grv being the term by which they designate 

 snow saturated with, or swimming in water. I shall venture to use 

 their term for the ice formed at the bottom. 



It will be better here also to state, generally, the conditions of 

 temperature and phases of the weather under which the ground-gru 

 is formed. I have seen it occur only when the temperature of the 



