334 REV. JAMES FARQUHARSON ON THE ICE 



reaching- it with the end of a pole, its consistency was found to be less firm ; in fact, 

 it was only a heap of detached uncemented spiculse pressed against the stones, and 

 retained there mechanically by the action of the water, in a certain modified state 

 of its velocity. The source of these heaps of uncemented spiculse will soon be no- 

 ticed. This pool, as indeed was the case with all the pools in the river, had at its 

 edges and in its little bays narrow pieces of surface-ice, extending a foot or two from 

 the banks. 



The rapid immediately above this, not unlike that at the bridge, was covered at 

 the bottom with silvery gru, with one exception. The river was low at the time from 

 long-continued deficiency of rarn, and the water had deserted the south side of the 

 channel, leaving many little pools among the stones, communicating more or less 

 freely by irregular little currents with the main stream. The pools were covered over 

 with sheet-ice, and that with a thin opake deposit of hoar frost like snow. In the 

 little currents returning from under this ice there was no frozen matter. 



At the head of this rapid there is a pool much deeper and stiller than that above 

 the bridge-rapid already described. The depth is five feet, and the stillness such 

 that, at many points of it, there is no ripple or wave on the surface. None of the sil- 

 very cauliflower-like ice was seen on the bottom here ; but near the head of it, in a 

 modified state of the current pouring in from the rapid above it, there were, on the 

 faces of several large stones opposed to the stream, collections of uncemented icy 

 spiculse. 



The source of these collections was very readily observed in a great rapid imme- 

 diately above this. In that rapid the water has a much quicker descent than in the 

 others referred to. It is about a hundred yards long, and cumbered with many large 

 stones, over which, at many points, through its whole length, the water breaks with 

 a great deal of spray. Here an immense quantity of gru occupied the bottom, im- 

 peding much the course of the stream. At the time of observation many pieces of 

 this gru were seen edging up, and in some instances breaking quite away from the bot-, 

 tom, apparently by the increasing pressure of the water, as it became dammed back 

 by the increase of the gru itself. This at least was the appearance, although there 

 may have been another cause for the disengagement of it from the bottom, and that 

 is, the impeding, by the imperfectly translucent gru, of that radiation of heat from the 

 bottom which, I trust in conclusion to demonstrate, is the immediate chief agent in 

 the whole phenomenon. 



It is now to be observed, that a number of pieces of loose gru, the origin of which 

 was so r;learly ascertained at this last rapid, were floating down in all parts of the 

 river. In passing through the rapids, they were broken into fragments, and, where the 

 fall was violent, shivered into minute pieces. The larger pieces that remained after 

 passing through the rapids floated at the surface, immediately as they got into the 

 uniformly flowing currents at the heads of the pools ; but the minuter ones, mixed with 

 the water to all depths by the plunging whirls in the rapids, not being so speedily 

 „<.„„„]^^ from their cohesion with the water, by the action of ern'^^v floatpH 



