Vol. 54.] EBBUfG AND FLOWING "WELL AT NEWTON NOTTAGE. 305 



of chlorine (and therefore of salt) seems to point to the fact 

 that some salt water must come into the well by the ordinary 

 process of diffusion, sufficient to render the well-water slightly 

 brackish, though this is quite imperceptible to the taste. 



The results of the analysis are set forth below, and I may mention 

 i;hat they are in close agreement with an analysis made of the same 

 water a few years ago by Dr. A. Yoelcker, the details of which 

 were furnished to me by the kindness of Mr. Edward Knox, of 

 the Estates Office, Margam Park, by whose direction the analysis 

 was made (see Postscript, p. 306). 



Analysis of the water of a well at IjTewton Nottage, collected 

 on October 8th, 1897. 



[The results are expressed in parts per 100,000.] 



Total solid residue 80 



Chlorine 16*4 



[Corresponding to 27'2 parts of sodium chloride.] 



Sulphates (the sulphate radicle, SO^) 5-15 



Calcium ,. 110 



Magnesium 0*76 



Hardness, — 



Temporary 228° 



(on Clark's scale, 16°) 



Permanent 17*2° 



(on Clark's scale 12°) 



Total hardness 40° 



(on Clark's scale, 28°) 



The interpretation of the observations detailed above does not 

 seem to present any serious difficulty. It is clear that there is, as 

 already mentioned, a large body of water contained in the basin of 

 Keuper conglomerate which overlies the Carboniferous Limestone 

 between the ancient sea-cliff immediately north of the village of 

 Newton and the present shore-line. This underground water is in 

 free communication with the sea, along the line where the conglo- 

 merate crops out below high- water level on the shore. 



The tidal wave, on reaching this outcrop, is taken up by the 

 water in the permeable strata and propagated landwards, but with 

 a greatly diminished velocity, owing to the resistance to its motion 

 offered by the solid, though porous, stratum of conglomerate. This 

 retardation is sufficient to cause an interval of 3 hours to elapse 

 before the successive phases of the wave (that is, crest and trough) 

 reach a point 500 yards from the line where the free wave stops 

 and the subterranean wave begins. Hence we have high water in 

 the well 3 hours later than high water in the sea, and low water 

 in the well 3 hours after the time of low water in the sea : the 

 ' establishment ' (as hydrographers would call it) of the well being 

 3 hours later than that of Porthcawl. 



An illustration of a very analogous phenomenon may be adduced 

 from the science of optics. When a series of light-waves, travelling 

 in a medium of low refractivity, arrives at the surface of a medium 



z2 



