94 



Correspondence — Rev. 0. Fisher. 



which is called the Eidfjord, and is about three-quarters of a mile 

 below the lake. 



Between the lake and the fjord is the old delta of the river, rising, 

 I should say, 150 feet above its present level. 



The problem is, how can the delta be where it is, without the 

 lake being filled ? My explanation is that the lake has been filled by 

 the delta, and has been cleared out by a glacier. If this explanation 



be correct it has important bearings on the action of glaciers. I do 

 not think, from its position at the head of a branch fjord, remote 

 from the sea, where the tides must necessarily be weak, that what I 

 have called a delta can be entirely, or even mainly, a sea-beach ; 

 this point, however, might be investigated by someone who could 

 devote more time to the question. William Churchill. 



New University Club, St. James's Street, s.w. 



THE SUBMAEINE CRUST. 



Sir, — It is obviously a matter of interest to obtain some know- 

 ledge, however slight, about the constitution of the earth's crust 

 beneath the great oceans. The fact that they are covered by a deep 

 layer of water, while it precludes the possibility of examining the 

 subjacent rocks directly, gives an opportunity for gaining some 

 information about them from considerations based upon their 

 attractive force upon the water itself. I have accomplished some- 

 thing in this direction in chap. xvii. of my " Physics of the Earth's 

 Crust," supplemented by chap. xxvi. added in an Appendix. 



In his " Introductory Keview " to " Annals of British Geology, 

 1893," Professor Blake has thrown a doubt upon my work. In fact 

 he has given it as his opinion that my calculations are unsound. 

 Your Magazine is not a suitable medium for a mathematical discus- 

 sion, but I hope you will allow me just to say, that I do not admit 

 the validity of any of the three objections he has formulated ; but 

 afSrm them to be altogether erroneous. 0. Fisher. 



Haulton, Cambridge. 



