Br. H. Landor — On Ground- Ice as a Carrier. 459 



VI. — Dk. H. Landor on Ground-Ice as a Carrier of Stones and 



Debris. 

 Communicated by James Geikie, F.E.S., L. & E., F.G.S, 



SOME years ago (November 15th, 1869) Dr. Henry Landor, 

 Superintendent of the London Asylum, Ontario, communicated 

 to the Entomological Society of Canada some observations on the 

 action of Ground-ice, which seem to be of sufficient importance to 

 be reproduced in the pages of this Magazine. The Entomological 

 Society does not appear to publish its transactions, otherwise a simple 

 reference might have sufficed. The account of Dr. Lander's obser- 

 vations here given is extracted from the local Free Press, of London, 

 Ont. 



" Ground-ice is that ice which is formed at the bottom of running 

 streams, and which adheres to the bottom for a greater or less length 

 of time, and which is often seen floating down all the rivers of 

 Canada in small pieces after a severe night's frost and a sunny 

 morning. There have been many theories given by men of science 

 to account for the formation of ice on the bottom of rivers running 

 rapidly. It has engaged the attention of men of such eminence as 

 Arago, but I think no theory has been given which will account for 

 all the phenomena. The facts are few and simple. When the ther- 

 mometer falls to within 10° of Fahrenheit, ground-ice begins to 

 form, but it is not, at that temperature, long adherent to the bottom. 

 As soon as the sun rises, it rises and floats away in great abundance 

 of small light porous portions of ice, covering for the most part the 

 centre of the stream. But when the thermometer is at zero, the ice 

 adheres to the bottom, and it is most apparent where the stream is 

 the most rapid. It is then most abundant where there is no surface- 

 ice. There is none where the surface is frozen over. Depth of the 

 stream, at any rate to six feet, if it is rapid also, does not prevent 

 the formation of ground-ice ; for it is seen abundantly on the bottom 

 of the St. Lawrence rapids, and at the Tubular Bridge, Montreal, 

 which affords a favourable point for observation, before the surface 

 is frozen over. As the frost continues, the ice at the bottom thickens. 

 It is tubular, or honey-combed, in the direction of the current, and 

 the water pours through the tubes. It is rarely solid, but it is so 

 after long continuance of hard frost. It adheres to the stones at the 

 bottom, or to the ground itself, and it remains anchored until its 

 power of flotation enables it to rise to the surface, and carry its 

 anchor with it. It comes to the surface with stones attached to it. 

 These stones, of course, bear a proportion to the mass of ice. When 

 the mass is small, the stones it raises are small, and are only 

 pebbles ; but when the mass is large — and it often is a large mass that 

 rises to the surface — it brings adherent to it large stones, deserving 

 to be called small boulders. The mass floats away down the stream 

 to the next part of the river that is frozen over at the surface. There 

 •it becomes frozen in with the mass of surface-ice, and in a very few 

 hours loses its porous condition altogether. It remains there until 

 the break-up of the winter, and it is then impossible to say whether 

 the stones in the ice were thrown on the surface and then frozen in, 



