April i,, 1872] 



NATURE 



45; 



Instances occur from time to time to point out isolated con- 

 sequences of this pernicious practice, but I believe no one who 

 has not gone into the geological question can realise its magni- 

 tude. It is not confined to one district or to a few towns or 

 villages. It is the rule, and only within the last few years have 

 there been any exceptions. The organised supply of water now 

 furnished by companies in all large towns has, to a great extent, 

 done away with the evil in those situations (though the root of 

 the mischief has too often been left unextracted) ; but in villages 

 and detached hou'ses, great or small, it remains untouched and 

 unchecked. Not a county, not a district, not a valley, not the 

 smallest tract of permeable strata, is free from this plague-spot. 

 It haunts the land, and is the more dangerous from its unseen, 

 hidden, and too often unsuspected exiitence. Bright as the water 

 often is, without objectionable taste or smell, it passes without 

 suspicion until corrupted beyond the possibility of concealment 

 by its evil companionship. Damage, slight in extent, or unim- 

 portant possibly for short use, but accumulative by constant use, 

 may and does, I believe, pass unnoticed and unregarded for 

 years. Nevertheless the draught, under some conditions, is as 

 certain in its effects, however slow in its operation, as would be a 

 dose of hemlock. Go where we may, we never know when the 

 poisoned chalice may be presented to our lips. The evil is self- 

 generating ; for the geological conditions supplying our neces- 

 sities lend themselves to its maintenance and extension. The 

 knowledge necessary to remedy it is of very slow growth, and the 

 too frequent want of that knowledge, or disregard of the subject, 

 even amongst able architects and builders, is such that, without 

 legislative enactment, I do not see how the evil is to be eradi- 

 cated for many a long term of years. 



This also is only one form of the evil — it is that where the 

 water-bearing strata are thin and the wells do not exceed a depth of 

 thirtv feet. It was the one which prevailed in London, and, in 

 town's similarly situated, up to a very few years back. It even 

 still lingers on in some private wells, and is moreover fostered 

 among us by the bright-looking and cool water of too many of 

 our public pumps ; for not only does the ground still suffer from 

 the effects of the original contamination, but also from much, 

 almost inevitable, obnoxious surface-drainage, much gas escape, 

 much rainfall on old open churchyards, which find their way to 

 the one level of water supplying in common all these shallow 

 wells. The evil still exists also, although to a less extent, in 

 towns where the wells have to be carried to much greater depths ; 

 its effects varying according as the depth, and as the volume of 

 the springs is to the sewage-escape ; it is, however, only a ques- 

 tion of degree. 



But even our deeper and apparently inaccessible springs have 

 not escaped contamination. As before mentioned, the under- 

 ground water will, when tapped by artesian wells, rise to or above 

 the surface, according to the relative height of the surface of the 

 ground at the well, and of the outcrop of the water-bearing bed 

 or beds, so that if the former is higher tlian the Hatter, or if by 

 artificial means the line of water-level in a given area becomes 

 lowered, then the surface of the water belonging to those great 

 underground natural reservoirs will be established accordingly at 

 a certain fixed depth beneath the surface. As each well deriv- 

 ing its supply in a stratum of this description represents a column 

 of water communicating with one common reservoir, it fallows 

 that any cause permanently lowering the level of one well will 

 tend to lower the level in the other wells in proportion to their 

 number and distance. Further, it has been discovered that a well 

 of this class can absorb a quantity of water equal to that which it 

 can furnish ; and as these wells give greater supplies than shallow 

 wells, the absorbing wells of the same class are alike powerful in 

 proportion to the others. The perverse ingenuity of man has 

 here, again, taken advantage of these conditions to get rid of 

 offensive waste waters by diverting them into such deep wells, 

 whence they pass away in hidden underground channels, unseen 

 and unsuspected, and mingle with those deep-seated water-sources 

 feeding the artesian wells dependent upon them for their supply. 

 In Paris, where there are several alternating beds of permeable 

 and impermeable strata, and the deptli to reach them is not 

 very great, this system of absorbing wells connected with fac- 

 tories became, until regulated by the municipality, very common, 

 to the great injury of many of the underground springs. From 

 this and the other causes before alluded to, a great number of 

 shallow wells have there become so contaminated as to necessi- 

 tate their abandonment. Our own system of surface-drainage is 

 generally too good, and the depth to the lower water-bearing 

 strata too great, to have rendered the use of such wells here 



equally advantageous ; nevertheless, I have reason to believe 

 that they do exist, and that the sources even of our deep well- 

 water supply in the Lower Tertiary Sands and in the Chalk are 

 thus to some extent polluted and injured. 



Nor do the great and perennial springs supplying our rivers 

 altogether escape the evils arising from tliese obnoxious practices. 

 On the high Oolitic ranges and amongst the undulating Chalk 

 hills, the line of water-level is often so deep below the surface, 

 that only in few cases are wells made — the population being 

 generally dependent on rainwater for their water-supply. But 

 this does not prevent the construction of dry wells for the dis- 

 posal of sewage and refuse. It is ti-ue that the population in 

 these hills is sparse — here and there a farm, a few cottages, and 

 scarcely a village. Still as the ground is everywhere absorbent, 

 and there are no streams even in the valleys (I am now speaking 

 of the higher districts), every dwelling contributes its quota ; for 

 the rain and all liquid matter absorbed in these strata necessarily 

 pass down to the great underground reservoirs of water feeding 

 the springs thrown out in the deeper river-valleys. In these 

 cases, however, the thickness of strata through which any liquid 

 has to pass before reaching the line of water-level is such as to 

 produce a more or less efficient filtration and complete decom- 

 position ; and as the injury caused is in proportion to the relative 

 volumes of the water-sources and to the artificial additions, the 

 great extent and dimensions of these water-bearing strata and 

 the scanty population of such districts reduce it to a minimum. 



Owing to these conditions, great as the evil is, expeiience 

 teaches that it has, in some cases, its vanishing-point. It may 

 be considered at its maximum in some of the wells of Paris ; our 

 own London shallow-well pumps follow next in order ; in our 

 river-waters away from towns it is but sbght ; in some of the 

 springs of the Chalk and Lower Greensands it is hardly appre- 

 ciable, while in the deep well-waters, especially those of Caterham 

 and Gienelle, it sinks to the_ minimum attained by any potable 

 waters, with the exception of rain-water. It is also a fortunate 

 circumstance that the wonderful powers of oxidation possessed by 

 air and water, and the powers of absorption and decomposition 

 by soils and earths, are such as, even in the surclrarged gravel-bed 

 of London, to remove all the more offensive characters, and leave 

 its spring-waters at all events limpid and bright ; whilst the 

 quick eddy, the moving ripple, the bright sunshine, the brisk 

 breeze, the Uving organisms, are ever at work in our rivers de- 

 stroying the almost inevitable accompaniments of the presence of 

 man, and restoring the waters to that original state of purity so 

 essential to his health and welfare. 



It was on considerations of quantity of supply thus dependent 

 on geological conditions, and of quality as dependent j intly on 

 geological and artificial conditions, that the Commission was 

 mainly so long and assiduously engaged. With legard to the 

 character of waters as dependent on the geological nature of the 

 strata, while the evidence showed that the waters flowing off 

 hard and insoluble rocks were, from their much greater freedom 

 from mineral matter, more economical for many domestic and 

 manufacturing purposes, yet that for drinking purposes, waters 

 such as those derived from our Chilk and Oolitic districts were, 

 on the whole, as good and wholesome as those from any other 

 sources ; while as regards quantity and permanence, the condi- 

 tions presented by a large catchment basin of a varied geological 

 structure presented the most favourable conditions for the large 

 and maintained supply so essential for a great city. And if, 

 from any cause, it should at some future time be thought desir- 

 able to have a supply of a yet more assured and undoubted 

 quality than a river supply, tlie large springs of the chalk and 

 the Lower Greensand, or the great underground reservoirs of 

 the most efficiently filtered water stored in those formations in 

 Surrey and Herifordshire, might, I believe, be resorted to with 

 advantage, by means of ordinary and artesian wells, as auxiliary 

 sources of supply for domestic and drinking purposes, supposing 

 the engineering difficulties connected with a double water-supply 

 could be overcome — a difficulty which it, however, seems to me 

 would possibly be less one of construction to our engineers than 

 of cost to the public. But in a great health-question there arc other 

 considerations than these which are of more primary importance. 

 ( To be continued. ) 



SCIENTIFIC SERIALS 



Joui-nal of the Franklin Institute, November 1871.— The 

 editorial notes in this number are as usual very instructive ; 



