162 Wisconsin Academy of Sciences, Arts, and Letters. 



water below the ridge also freezes. When at a later warm time 

 ice expansion again comes the ice ridges form at some other 

 place. This gives a cine to the manner in which new mountain, 

 ranges may be formed. After a first mountain mass with ac- 

 companying vulcanism has formed, and there has been a long 

 period of quiescence, in which the lava at the surface and filling 

 the openings in the crust has solidified, the rigidity of that por- 

 tion of the crust of the earth may be greater than at some ad- 

 jacent place, and when later thrust accumulates so that deforma- 

 tion is necessary it finds relief at some other area. However, 

 it is to be remembered that in many cases mountain-making 

 movements along the same axis have recurred repeatedly, and 

 this would be expected, provided there were not long periods be- 

 tween the successive movements. 



Dr. Buckley notes that expansion producing ice ridges fre- 

 quently follows contraction. The contraction produces tensile 

 ruptures. When expansion follows, the ice ridges are located by 

 these tensile cracks. The question naturally arises whether or 

 not the same thing may frequently be true for crustal deforma- 

 tion. 



In conclusion I may say that the phenomena which Dr. Buck- 

 ley has so well described seem to me to reproduce on a larger 

 scale than has been possible by experiments in the laboratory 

 many of the phenomena of crustal deformation ; and, moreover, 

 that the analogies are so astonishingly close as to lead to the con- 

 clusion that in most cases crustal forces have acted in a similar 

 manner to those in which the forces in the ice have acted, al- 

 though the ultimate cause of the force in the two cases is mainly 

 different, that of the ice being expansion or contraction due to 

 change in temperature, while that in the earth's crust is that of 

 gravitative stress caused by the earth's contraction, which comes 

 from various causes, including change in temperature. 



