164 



ON THE OBIGIN OF MOUNTAIN EANGES. 



about 120° Tah. I should like to seo a calculation of tlic 

 number of units of boat lost to tbo under- strata annually 

 through the instrumentality of hot springs. I believe it to 

 bo one of the functions, and not the least important func- 

 tions of water to be constantly diving into the earth cold 

 and rising to the surface in a more or loss heated condition. 

 I am not aware whether this has been ever sufficiently 

 taken into consideration. It seems to me to be a highly 

 important agency by which the underlayers of the crust 

 are made to cool and contract more rapidly than the over- 

 layers. It may help too to account for the diminished 

 temperature beneath mountain ranges ; the diminished den- 

 sity beneath continental as compared with oceanic areas 

 being explicable on that hypothesis of dilTorcntial cooling 

 along different radii which accounts for the initial deter- 

 mination of these oceanic and continental areas. 



In conclusion, I would beg to draw the attention of the 

 members of this section to the many valuable facts and 

 illustrations of mountain structure which Mr. Mellard Reade 

 has collected together in his volume. I do not think his 

 theory will be generally accepted. But then arc wo not all 

 of us much in the dark on this difficult question ? Might 

 not some good-humoured cynic liken our attempted solu- 

 tions to the sweet twitter of the sea-lark in Browning's 

 song, mountain ranges being but part of the " good gigantic 

 smile of the brown old earth " ? 



" Oh, good gigantic smile of the brown old earth, 

 Thia autumn morning 1 How he sets his bones 



To bask in the sun, and thrusts out knees and feet 



For the ripple to run over in its mirth : 

 Listening the while, where on the heap of stones 



The white breast of the soa-lark twitters sweet I " 



