SO^ ItE. fi. G. MADAN ON AN ifiBBlNG AND [Aug. iSpS, 



thick. This rests on the conglomerate, into which the cutting did 

 not penetrate far, so that I was unable to ascertain the thickness of 

 this bed. The strata are nearly horizontal, perhaps with a very 

 slight westerly dip, and the conglomerate seems to thin out to 

 nothing at Porthcawl itself, where I noticed in a cutting along one 

 of the streets, first 1 foot of sand, below it 2 to 5 feet of brown clay, 

 and then hard limestone, the surface of which was very irregular 

 in level, evidently a denuded shore. The conglomerate appears 

 again westward of Porthcawl, but I saw no object in tracing it 

 farther for my present purpose. 



At the base of this stratum of conglomerate, where it rests upon 

 the Carboniferous Limestone, there is evidently a considerable body 

 of water flowing southward and seaward, as is proved by the 

 existence of several fresh- water springs which burst out along the 

 shore due south of Newton Nottage at about half-tide level. It is 

 this underground water that is tapped by the public well which I 

 went to examine, and also by several other wells in the village, now 

 covered over and provided with pumps. 



The ancient dipping-well itself is an oval pit, 6^ feet in its 

 longest and 4| feet in its shortest diameter. The depth of the 

 bottom of the well from the surface of the ground is 13| feet, and 

 the walling is continued for about 2 feet above the ground-level, 

 and covered in by slabs of stone. Access to the well is afforded by 

 a covered flight of twenty steps, 27 feet long. There is an 

 Ordnance temporary bench-mark on the stone slab covering the 

 entrance to the passage, from which it appears that the bottom of 

 the well is 8 feet above Ordnance datum-level. The distance of the 

 well from the shore (high-water mark) is 500 yards, as deduced 

 from the mean of several pacings of the interval. 



The point which I wished especially to ascertain was the exact 

 relation (if any) of the variation in level of the water in the well to 

 the rise and fall of the tide. For this purpose it was necessary, — 



(1) To ascertain the exact times of high and low water. This 

 information I obtained from the harbour-ofS.ce at Porthcawl, the 

 distance between Porthcawl harbour and the shore at JN'ewton being 

 so small (about 1 mile) that the tide-table is practically the same 

 for both. 



(2) To measure the exact depth of water in the well at short 

 intervals between the time of high water and that of low water. 

 This was done by lowering a white deal rod vertically into the 

 water until the lower end rested upon a marked spot on the lowest 

 step, which was within an inch or two of the bottom of the well. 

 On withdrawing the rod it was easy to note the exact boundary 

 between the dry and the wetted portion, and a line was at once 

 drawn there with a pencil, the date, hour, and minute being 

 appended. The distance between the mark and the lower end of 

 the rod was then measured with a foot-rule, the result giving the 

 depth of water above the lowest step at the time of observation. 

 The mean actual variation in level was about 30 inches. 



