426 



NA TURE 



[March i, 1906 



The Brithidir — in some parts called the Tillery — seam 

 of coal constitutes the dividing plane between the Pennant 

 Sandstone and the Lower Shale series. 



In a section taken at right angles across the valley at 

 the point where the landslide — the subject of the present 

 notes — is taking place, that is, about one and a half miles 

 higher up the stream than the point at which the Brithidir 

 seam dips under it, the bottom of the valley is 750 feet 

 wide and 700 feet above sea-level ; the outcrops of the 

 Brithidir seam are 3000 feet apart and 1000 feet above 

 sea-level, and the summits of the Pennant Sandstone are 

 about one and a half miles apart and 1300 feet above sea- 

 level. The average inclination from the outcrop of the 

 seam to the bottom of the valley on each side is thus 

 approximately 1 in 4. 



Above the outcrops of the seam the ragged edges of the 

 sandstone escarpments are seen projecting above the 

 accumulations of debris which hide their bases ; below the 

 outcrops a superficial, grass-grown deposit, partly perhaps 

 nf Glacial origin, consisting of earth, clay, sand, and 

 stones, probably not more than from 10 feet to 20 feet 

 thick at any point, and possibly thinner in many places, 

 lies upon and entirely conceals the shales. Part of this 

 deposit, having a width of between 2000 feet and 3000 feet 

 measured along the line of the valley, is known to have 

 been slowly moving down the western slope ever since 

 the Rhymney Railway was constructed across it, near the 

 bottom of the valley, some fifty years ago. The excessive 

 slowness of its general motion is shown by the following 

 facts : — first, the railway, together with a stone bridge 

 over it. has only been carried to a distance of from 6 feet 

 to 10 feet eastwards from its original position during the 

 whole of that long period of time ; secondly, the arch of 

 the bridge, which, although damaged and partially dis- 

 torted, was prevented from being entirely broken up by 

 placing heavy balks of timber between its side-walls 

 under the level of the rails, was only removed, and re- 

 placed by a girder bridge, three years ago; lazily, tie 

 river, which flows at the foot of a steep bank, not far from 

 the railway bridge, has retained its old channel, and has 

 been able to carry away the debris from the foot of the 

 moving bank sufficiently fast to prevent the latter from 

 invading its bed. 



Although the general movement of the ground is so slow 

 and uniform that the roads and fences, and the vegetation 

 which grows upon the surface, give no clue as to what 

 is taking place over the greater part of the affected area, 

 there are local indications here and there which show thai 

 a number of smaller and comparatively rapidly moving 

 landslides have occurred within the larger area from 

 time to time. One of these smaller landslides recently 

 damaged the village of Troedyrhiwfuwch, situate near 

 the upper end of the moving slope. This village consists 

 of a public house, a school-room, and two rows of twenty 

 or thirty houses, built upon the opposite sides of a road 

 which runs parallel to the valley at a height of about 

 200 feet above the river. The pine-ends of many of the 

 houses, in the row nearest the centre of the valley, appear 

 to have lately undergone substantial repairs, and the 

 publii house has been entirely re-built, with its found- 

 ations, it is said, now resting on the solid rock. J he- 

 gardens of the houses nearest the northern end of the row 

 now under consideration, together with the division walls 

 between them and the outhouses contained in them, have 

 been ruined beyond repair, and part of the ground on 

 which the gardens were formed has been broken and piled 

 up behind the houses like the front of a wave advancing 

 down the slope, and appears to be still moving. 



In this part of the coalfield, as well as over practically 

 the whole of Monmouthshire and part of East Glamorgan- 

 shire, the strata immediately underlying the Pennant 

 Sandstones consist of a succession of red and blue shales 

 and marls of greater or less thickness. In the New 

 Tredegar pils, which are not far from this locality, the 

 red and blue ground has a thickness of more than 300 feet. 

 This is, therefore, the kind of ground upon which the 

 landslide is taking place. But as most strata of this kind 

 disintegrate and soften when exposed to air and moisture, 

 it is not improbable that this property of theirs accounts, 

 to some extent at least, fur the gradual movement of the 

 deposits lying upon them on the west side of the valley, 



and that it may be likewise responsible for the more 

 sudden landslide that took place a year or two ago on the 

 opposite side of the valley, which seriously damaged both 

 the Brecon and Merthyr Railway and one of the Powell 

 Duffryn collieries which lay in its path. 



My thanks for information concerning the Rhymney 

 Railway and the bridge over it are due to Mr. Cornelius 

 Lundie, formerly general manager, and now consulting 

 director, to the railway company, who has known, and has 

 had occasion to observe, the movements taking place in 

 this locality for the last forty-five years, and is therefore 

 thoroughly conversant with the subject. 



W. Galloway. 



NO. 1896, VOL. J 3] 



THE LAW RELATING TO UNDERGROUND 



WATERS. 

 T N one of the State papers recently issued by the depart- 

 ment of the United States Geological Survey there is 

 a report by Mr. D. W. Johnson dealing with the rights 

 of landowners and others to underground waters, for the 

 purpose of giving the owners of such waters some idea of 

 their rights and obligations. 1 



rhe report is not intended to be a legal treatise, but as 

 a practical guide for the officers of the hydrological depart- 

 ment, showing the relation of the law to problems which 

 are of a more or less hydro-geological character. 



The law relating to underground waters in the United 

 States is practically the same as in this country, and the 

 decisions given in the courts there are founded on British 

 precedents modified in some cases by the different circum- 

 stances of the two countries. 



Underground water is held to comprise all water which 

 for the time being is below the surface of the ground, 

 whether by penetration of the rainfall or soakage from 

 rivers and lakes, and which is dissipated throughout the 

 mass of porous soil or rock, except in cases where the 

 underground water can be traced as moving in a well 

 ascertained and definite course that can be located. 



The fundamental principle upon which the laws regu- 

 lating the use of underground water is formed is this : — 

 That such percolating subterranean waters are a part of 

 the land itself. The land belongs to the owner, whether it 

 be rock, porous ground, earthy matter, or part soil and 

 part water, the water being as much his property as rock, 

 ores, or minerals. Consequently, he may take and use 

 such waters as he pleases, even though such use may 

 damage his neighbour by removing or diminishing water 

 from adjacent wells or springs, by causing subsidence to 

 land or buildings by abstraction of the water, or by render- 

 ing the water useless by pollution from sewage or refuse 

 from factories or mines, &c. 



This principle has been admitted in the decisions given 

 by the courts owing to the difficulty of proving how much 

 of such water was within the limits of any given area, how 

 much comes from adjacent land, or how much passes from 

 one man's land to that of his neighbour, and the im- 

 possibility of predicting what result may ensue from inter- 

 ference with what has been regarded as an unknown 

 quantity. There are, of course, local circumstances or con- 

 ditions which modify this general statement, but, broadly, 

 this is how the law stands at present. 



In the United States, however, conditions have for some 

 time past been undergoing an alteration, and the investi- 

 gations and observations undertaken by the hydrological 

 department of the Government have been throwing con- 

 siderable light on the action of underground waters. In 

 many cases the original lack of knowledge which was the 

 reason for the ruling of the law as it now stands has 

 already disappeared. 



We recently gave a short illustrated description of the 

 methods adopted by surveyors of the department for 

 measuring and defining the rate and direction of the How, 

 and more particularly for showing the effect of percolation 

 of deleterious matter from factories, oil wells, &c, on the 

 underground supply of drinking water (Nature, December 

 21, 1905). 



1 " Relation of the Law to Underground Waters." By D. W. Johnson. 

 Water Supply and Irrigation Papers, No. 122. (Washington: Government 

 Publishing Office, 1905.) 



