[BARNES] ANCHOR-ICE FORMATION 97 



above its former level that it covered deeply the pieces of sheet-ice 

 formed at the edge of the 5th. 'New pieces of similar ice were now 

 forqiing at the same places on the more elevated surface. The Leochal 

 was still more impeded by the gru than the Don. 



But, what is worthy of particular notice, the clear spaces of the 

 bottom, at the piers, abutments, and embanking-walls of the bridge 

 on the Don, and at the Phalaris grass in the Leochal, still continued 

 so, but were now considerably narrowed in their lateral dimensions, the 

 gi'ound-gru having encroached upon them on the sides next the steams. 

 The temperacure of the air was 24° Fahr. ; of the water, everywhere 

 nearly steady at 32"^. 



►Several circumstances occurred on some subsequent days which 

 deserve to be noticed, as throwing light, by the contrast which they 

 exhibit, on the phenomenon now under consideration. On the 8th of 

 January there occurred a thaw, when the thermometer suddenly rose 

 to 47° Fahr. The rivers were speedily cleared of ice and ground-gru, 

 which last rose from the bottom and floated away with the steam. 

 The atmosphere at the time was considerably clouded, with a brisk 

 S.W. wind. On the 9th of January the temperature of the air fell 

 to 36° Fahr. ; and on the morning of lOth of January, with a tem- 

 perature of the air at 29° Fahr., there was a fall of snow, of about 

 an inch deep, which ceased by 8 o^clock a.m. The snow that fell 

 into the rivers was observed to be entangled, and stuck fast, in irre- 

 gular crushed masses, in many parts of the rapids; and there were 

 collections formed of loose spiculfe of a miiddy aspect, at the sides of 

 the stones opposed to the streams in the heads of the pools, where 

 the velocity of the currents was intermediate between that of the 

 rapids and that of the stiller parts of the pools; but there was no 

 appearance on any part of the bottom resembling the symmetrica] 

 cauliflower-shaped ground-gru. On the evening of the 10th the tem- 

 perature of the air fell to 23°, and continued at from 23° to 21° till 

 the morning of the 12th, with a densely clouded state of the sky. 

 During this time extensive sheets of surface-ice were formed on the 

 pools of the Don, and many of the pools of the Leochal were quite 

 frozen over, but the ground-gru was nowhere renewed ; on the contrary, 

 the masses of snow entangled in the rapids on the 10th disappeared 

 to a great extent, obviously floating away in the stream. In this 

 state of the river and weather, the collections of uncemented spiculae, 

 on the faces of the stones opposed to the streams in the heads of the 

 pools, appeared in their places the same as before, neither increasing 

 nor diminishing in size. 



Sec. III., 1906. 7 



