A. B. Sunt — Geological Physics of the Shallow Seas. 321 



placed on the axis of the deposit, when the true shape can be seen 

 much better (see Plate XVIII, Fig. 1). 



The photograph accompanying this note was taken from this 

 axial point of view ; the ridge of sand and clay is, of course, much 

 foreshortened. (The height of section shown is about fifteen feet.) 

 Owing to the uniformity of colour of the chalk and the fact that 

 most of the joint faces were equally illuminated, it was necessary, 

 in order to get a clear diagram, to go over every line visible with 

 waterproof ink, afterwards partially bleaching the print; at the 

 risk of making the diagram confused every line visible on the print 

 in a good light was marked, whatever its direction. 



The cylindrical joints can be fairly easily seen; the I'adial joints 

 are best seen to the left of the central line ; the faces formed by the 

 transverse joints are directed towards the camera, so that the joints 

 themselves are not visible. 



A simple explanation of the formation of the three sets of joints is 

 provided by the fact that chalk is soluble. After the channel of the 

 stream became choked by deposit, and the waters were forced to run 

 elsewhere (possibly through the other small channels visible on the 

 same level), the chalk by long-continued solution slowly contracted, 

 while beyond a certain point the gravel and clay would not contract. 

 Under these conditions it is clear that three sets of joints would be 

 ■ formed round a solid rod-like axis if the contracting material were 

 homogeneous. 



PUte XVIII, Fig. 2, shows the structure of the chalk round 

 two of the smaller deposits which occur on the same level in the 

 pit; this photograph has been treated in the same way as the first. 

 A similar explanation of this case seems to be possible, though its 

 application is not quite so easy. Owing to the band-like shape of 

 the deposits the chief joints radiate from points at the ends of the 

 bands, looping from one point to the other, thus producing a figure 

 somewhat like the lines of force of a simple magnet. 



VII. — The Geological Physics of the Shallow Seas. 

 By A. E. Hunt, F.L.S., F.G.S. 



SINCE the year 1871 I have been much impressed with the 

 interest and importance of one of the byways of science, 

 the problem of the Geological Phj'sics of the Shallow Seas. 

 Eecent discoveries in I'aised beaches have brought this subject 

 again to the front, and the object of the present paper is to plead for 

 further inquiry by specialists. 



I may briefly mention my own now antiquated papers, viz., 

 " Notes on Torbay " (Trans. Dev. Assoc, 1878) ; " The Formation 

 of Eipple-mark" (Proc. Roy. Soc, 1882) ; "The Action of Waves 

 on Sea Beaches and Sea Bottoms" (Roy. Dublin Soc, 1885) ; and 

 " On the Influence of Wave-currents on the Fauna inhabiting 

 Shallow Seas " (Journ. Linn. Soc, 1884). With the exception of 

 the Dublin paper, the MSS. were, as a matter of fact, perused by 



DECADE V. — VOL. II. — NO. VII. 21 



