70 ROYAL SOCIETY OF CANADA 



clear sky at night. Anchor-ice is readily melted off under a bright 

 sun. It seems highly probable then that radiation of heat supplies 

 the necessary cooling to the bottom of a river to establish the first layers 

 of ice, after which the growth or building up of the ice is aided by 

 the entangling and freezing of frazil crystals always present in the 

 water. 



The growth of anchor-ice is exceedingly beautiful, taking place 

 in arborescent forms, resembling bushy weeds. So hard does it be- 

 come and thick that it is often very difficult to thrust a sounding rod 

 through it. It is very granular in structure, as is shown by an exam- 

 ination of the masses which rise to the surface. Through clear water 

 the ice looks weed-like, with long tentacles rising up out of the 

 mass. It often has iinm.ense power in lifting rocks and boulders, 

 and many of these are carried far down stream attached to irregular 

 masses of ice. The spongy character of adhering frazil crystals and 

 anchor-ice causes them to accumulate slime and infusorial growths from 

 the water. A very characteristic colour of these masses is brown. 

 When melted in a vessel the slime settles to the bottom, when it is 

 seen to be of a very fine structure, 



APPENDIX. 



Some Early Memoirs on Ground-ice. 



During my search through the literature on natural ice formation 

 it" was my good fortune recently to discover four important and inter- 

 esting papers written many years ago, at a time when scientists 

 apparently first turned their attention to the formation of ice on 

 the bottom of a river. I consider these papers are of such im- 

 portance on account of the mass of observations they contain that 

 I reproduce them here in full by the kind permission of the 

 Publication Committee of the Koyal Society. The value of these 

 papers will be at once apparent to anyone reading them, and the fact 

 that they have remained practically unnoticed for upwards of seventy- 

 five years renders them all the more interesting, I have never seen 

 them referred to by modern writers on the subject of river-ice formation, 

 and it was only by the merest chance that it was my good fortune to 

 discover them. The volumes in which they appear, i.e., the Edinburgh 

 New Philosophical Journal, and the early Transactions of the Eoyal 

 Society of London, are now difficult to obtain, and in placing them on 

 record here, I feel confident that our knowledge of the causes under- 

 lying the formation of anchor-ice will be vastly increased. 



