Mr R. Adie on Ground-ice. 245 



land Hills, near Edinburgh, which come strictly under the term 

 ground-ice. Although they relate to ice in very different circum- 

 stances from what wo find in streams, yet they bear on the question 

 of nuclei for the crystals. After a showery day, the sky before mid- 

 night cleared, and a sharp frost suddenly set in ; next day there 

 were pools of water on the roads covered with cakes of ice \ of an 

 inch thick. On the sides of the hills where the rain-water had been 

 slowly oozing down, in the sheep-paths and places a little bare of ve- 

 getation, I observed innumerable ice-pillars rising, closely com- 

 pacted in beds, to heights varying from \ to 2 J inches ; the sides of 

 these pillars were white and striated, very much resembling the sec- 

 tions of the broken cakes of sal ammoniac of commerce, only not so 

 solid in texture ; they all carried capitals, composed chiefly of frag- 

 ments of stone, but pieces of earth or heath, or in fact anything that 

 could be raised, was elevated on these pillars. One small bed of them 

 was crossed near the middle of the pillars with two parallel bands of 

 coarse grains of sand; which appeared to me to shew that their growth 

 took place from the ground, and that the bands might be accounted foi 

 by some brief meteorological change, checking twice the formation 

 of the ice. The capitals appeared to be useful for the first start of 

 the pillars, for there were none without them ; but it is a gradual 

 regulated supply of water which has the most essential part to per- 

 form ; for where there is too much water the stones are frozen fast 

 down and do not rise. These ice-formations are, I find, familiar to 

 those who have walked on hilly undrained ground, during frosts. On 

 crossing over to the south side of the hill, the sun suddenly emerged 

 from behind a cloud, when it was interesting to observe the rapid de- 

 capitation of the ice-pillars which immediately commenced. The 

 portions of soil and plants which here served to begin a process so 

 active in ice-making, are never awanting in pools or running streams, 

 where they may be expected to be efficient in forming scales or spi- 

 culse. The overhanging banks of many mountain torrents may also 

 often off*er favourable places for soft ice so formed dropping into the 

 stream. When the thickness of solid ice-cakes is compared with the 

 length of the pillars, the rapidity of the latter in forming ice is ap- 

 parent. 



In the vicinity of the village ck' Altcar, 12 miles north of Liverpool, 

 there is a stream locally known by the name of the Altcar Brook, a 

 tributary of the river Alt, well adapted for examining ground-ice in 

 running waters of low velocity. The brook drains a flat open dis- 

 trict adjoining the Irish sea ; the ground is intersected by numerous 

 open ditches holding large quantities of water, coloured by peat of a 

 dark brown hue. The velocity of the current in the brook for two 

 short distances near its termination is from 2 to 3 miles per hour, 

 flowing smoothly along in a mud or sand bottom with small eddies. 

 Plants occupy the bed in patches : these in the winter season are all 

 covered with water to a depth of from 6 to 12 inches. The upper 



VOL. XLII. NO. LXXXIV.— APRIL 1847. B 



