462 Dr. H. Landor — On Ground-ice as a Carrier, 



siderable geological changes, distributed over large areas, and of 

 consequence in the estimate of geological conditions. Nor is the 

 effect of ground-ice confined to Canada. The rivers that flow into 

 the Northern Mississippi carry the same conditions into the south, 

 as far as the ice floats undissolved. But if this subject has a bear- 

 ing on geology, it has a far greater effect on the distribution of 

 species, both of plants and small living creatures, fresh-water shells 

 and insects especially. With the stones, portions of earth are very 

 frequently carried by the ice, and every mass of earth contains seeds 

 of land or water plants, which are borne down the rivers and distri- 

 buted wherever the mass of ice breaks up. Some of these ice- 

 bearing boulders and earths are driven on to the land at the sides of 

 the rivers or lakes, and there dissolve, and there the seeds germinate 

 and the insects flourish, perhaps planting species where they were 

 before unknown. Now consider the result of this operation on 

 rivers like the Mississippi, or the Saskatchewan, or the Mackenzie. 

 From a central area, the Mississippi and the Mackenzie distribute 

 species in opposite directions, some of which may be new to the 

 countries they rest in, and may be able to endure the difference 

 of climate. The Saskatchewan distributes west to east, from the 

 Eocky Mountains to Hudson's Bay. As it is most probable that 

 the Eocky Mountains emerged from the ocean before the plains to 

 the east or west of them, it is possible that, as vegetation and insect 

 life began in these mountains, both were mainly distributed over the 

 continent, as it gradually rose above the waters, by this very agency. 

 At any rate, if the climate was as it now is, this agency must have 

 borne a large share in the distribution of life over the land wherever 

 the streams from the mountains flowed. But these phenomena are 

 not confined to North America. The rivers of Siberia do the same 

 thing ; so do the rivers of Northern Europe. Therefore the effect 

 of ground-ice on the distribution of species over limited areas does 

 not deserve to be overlooked. I think these are the chief facts that 

 occur to me on this subject. I am not acquainted with any other 

 observations on this matter. It is not even alluded to in Lyell ' On 

 the Distribution of Species,' nor does Darwin notice it. I am desirous 

 that it should be further examined, and I send you this paper to 

 induce some of your members to take the subject up, and carry on 

 their observations in a combined manner, with proper means, which 

 can be more readily provided by a society than by an individual. 

 I do not pretend to anything more than a very limited amount of 

 observation, and my speculations may or may not be confirmed by 

 better and more scientific observers. I leave the matter in your 

 hands. I think this paper, on a new subject, is deserving of publi- 

 cation, if only to cause others to make more efficient examination." 



^^ Note. — The Thames is every year becoming more unfit for observations on 

 ground-ice. Less water comes down it, especially the north branch, so that the 

 shallows will hardly float ice that can carry a boulder. I saw more ground-ice in 

 the four winters from 1860 to 1864 than in the last six years. The Grand river I 

 should think more suitable for observation." 



Dr. Landor writes me this summer concerning some further 

 observations made by him as follows : " There is another fact 



