﻿466 Frof. Milne — Across Europe and Asia. 



new ones might be born. Not overlooking the observations of Pro- 

 fessor Agassiz on the Amazons, and those of Mr. Belt in Nicaragua, 

 evidences of this kind are yet very rare. As additional reasons for 

 not forming too hasty a conclusion, we must wait until the markings 

 of the ice-cap have been shown to be more general in their dis- 

 tribution, and the markings which would be consequent on such a 

 covering have been more fully recognized. Cosmical changes have 

 no doubt produced their effect upon climate, and so also have causes 

 like those we now see in action, and therefore I do not see the 

 necessity that all glacial phenomena should be attributed wholly to 

 the one or to the other cause ; but I must confess that where it is 

 possible to adopt existing agencies, I should take them into con- 

 sideration before those whose origin and subseqiient mode of action 

 was of a more debatable character. For these reasons, together 

 with the fact that the Siberian Steppes present phenomena not well 

 explained by the invasion of a polar ice-cap, I venture to suggest 

 a modification of the theory advocated by Mr. Belt and Siberian 

 geologists, which appears to me to be more reconcilable with the 

 phenomena which have been hitherto recorded. 



In addition to the general freshwater character of the plains which 

 has been already noticed, we must also observe the slight elevation 

 which i\\Qy have above the Northern Ocean towards which their 

 rivers flow. On physical maps points more than 1000 miles inland 

 are shown not to be more than 250 feet above it. Another point 

 to be observed is that the last movement which these plains have 

 made, as indicated by beds of marine shells along their northern 

 frontier, has been an upward one. From this we may infer that 

 when they were at lower levels a considerable portion of their 

 surface must have been covered by what would now be an invading 

 sea. At such a time the rivers would be shorter in length, and the 

 plains, through which they flow, more tongue-like in their character. 

 Again, we must observe that in old times, as at the present day, 

 these rivers were often covered with ice, which, blocking uj) their 

 channels, may have given rise to floods. These actions can now 

 be seen both at the forming and the breaking up of these winter 

 barriers. By comparison with what has happened in Europe and 

 in America, we may infer that either cosmical or geographical 

 changes, or perhaps both, have in former times intensified this 

 action. 



The following table, which I have compiled from information 

 collected when in Siberia, will show approximately the time of 

 formation and breaking up of ice at different latitudes upon the same 

 and different North Asian rivers, and will indicate an important 

 cause operating in the formation of these floods or temporary lakes : 



The first thing that will be observed in this table is that the 

 influence of latitude practically outweighs all local circumstances 

 which might accelerate or retard the time of freezing, or the break- 

 ing up of the ice upon these rivers. The farther north a place is, 

 the sooner the water freezes, and the later is the ice broken up, as 

 compared with more southern positions. Another point to be noticed 



