342 Mr. R. Adie on Ground Ice found in 



qualified sense. When water has different temperatures at dif- 

 ferent depths, for example, 35° at the bottom and 31° at the 

 surface, then it is easy to see that motion, by mixing the water 

 at 35° with the surface-water, must retard its freezing ; and this 

 is the state of our lakes, ponds, &c. But where the water from 

 rolling along the bed of a stream has one uniform temperature 

 of, say 31°'5, I apprehend the motion favours the formation Of 

 ice. In the experiment of cooling down still water below the 

 freezing-point, a rapid congelation is found to follow the shghtest 

 motion. 



The soft snow-like nature of ground ice is evidence in favour of 

 its being not formed in situ; for if ice be formed by artificial means 

 at the bottom of a vessel ojf water, it is of the hardest description; 

 I can see no reason why, in the bed of a stream where the motion 

 of the water is at a minimum, it should differ from that formed by 

 the artificial process. In this country, where the frosts are never of 

 very long duration, ground ice is in the form of a soft incohesive 

 mass; but in localities on the continent, where the winter is steady 

 and long, ground ice assumes a firmer compact form ; for the same 

 reason that newly-fallen snow, a loose mass ready to be driven 

 about by every wind, in process of time gradually passes into a 

 state of firm ice, as has been shown in the modern researches on 

 glacier ice. Another circumstance against the supposition that 

 ground ice is formed where it is found is, that in places favourable 

 for its reception the quantity found in the bed of the stream under 

 a depth of one to two feet of water is often greater than the 

 quantity of surface-ice on a like superficies of still water in the 

 same neighbourhood. Supposing the ice to be formed on the 

 bottom, the superincumbent body of water must act as a great 

 retardation. The effect of a light arch over a canal in checking 

 the freezing of the water underneath illustrates this. The quan- 

 tity of ice in the river-bed should thus be much less than the 

 surface-ice in the neighbourhood for a corresponding superficies, 

 which is often not the case. 



The streams best suited for exhibiting the phsenomenon of 

 ground ice are those which drain open exposed tracts of country 

 with few trees or tile-drains. From 10 to 12 miles north of 

 Liverpool, at Altcar, there is a flat country of this character : 

 the land is drained by a series of open slow running ditches ; a 

 portion of the water of these ditches is carried by a stream, locally 

 known by the name of the Brook, into the river Alt. The velocity 

 of the water varies from 2 to 3 miles per hour, depth 2 feet. 

 On the 11th and 12th of February 1853, the district was visited 

 by a severe frost, temperature 21°, with a sharp wind; on the 

 morning of the 13th I examined the locality, when I found the 

 bed abundantly covered with ground ice. The temperature ot 



