August 17, 191 1] 



NATURE 



23: 



tin- river, and supply the town only from (lie stored water 

 of the Ormesby Broad. Sir William Ramsay, too, invented 

 for the occasion a little instrument. It was a small glass 

 cell, containing two copper plates. This was to be sunk in 

 the river, and so long as the plates were in contact with 

 the fresh river water no electric current passed between 

 (fee plates. But when salt water was substituted for fresh, 

 and it was sufficiently salt to have 20 grains of chlorine 

 to the gallon, an electric current passed and rang a bell. 

 If this little apparatus was placed in the river two or three 

 miles below the intake, there would be timely warning of 

 the uprush of the sea water, and it was explained that it 

 could be made not only to ring a bell but to stop the 

 pumping-engine. This apparatus was exhibited to the 

 Lords' Committee, and, upon salt being- added to the water, 

 (fee bell rang. 



It may be of some use if I say something about the 

 sources and methods of supply. There is nothing very new 

 about water supply. Even in deep wells we have been 

 anticipated: Joseph's Well at Cairo is 297 feet deep, and 

 some of the wells in China have gone to a depth of 

 1500 feet. In modern times we have in some cases been 

 abandoning our well supplies. At one time almost the 

 whole supply of Liverpool was drawn from wells in the 

 New Red Sandstone. To-day she only draws 7.36 per cent. 

 from wells — 3642 per cent, from Rivington and 56-22 per 

 cent, from Vyrnwy. There is a well at Passy, near Paris, 

 H13 feet deep, and it delivers 5.' million gallons of water 

 a day. In South Dakota there is a well which penetrates 

 the earth's crust 725 feet and raises n j million gallons a 

 day. In relation to the purity of such underground 

 supplies, many of them in this country are derived from 

 the chalk, and it is interesting to note the precautions 

 which nature has taken to purify such supplies. It is 

 found that such soils as chalk breathe air and expel gases 

 just as the human lungs do. The breathing is long-drawn 

 and irregular, and depends mainly on the barometric 

 pressure of the atmosphere. But that such breathing takes 

 place can be shown by the simple experiment of closing the 

 folding doors over a chalk well and holding a lighted 

 candle to the bucket rope-hole, and the sensitive flare will 

 show the indraft or ouldraft as the case may be ; which 

 varies, of course in intensity according to the extent of 

 recent barometric changes. When water has to be got 

 from underground sources, then a well has to be sunk, 

 adits driven, a pump established, and the water raised to 

 the clear water-tank. In some cases, however, nature not 

 only does the purification of our water by its chalk lungs. 

 Inn does our pumping for us, as in the case of an artesian 

 well. 



But not only have we been anticipated in the matter of 

 wells ; in aqueducts we are mere imitators of our prede- 

 cessors, who even understood, it is obvious, the principle 

 of the inverted syphon, as it is called, by means of which 

 water is carried in pipes across valleys running down hill 

 on the one side and up hill on the other; for Lyons, in 

 France, was supplied long ago bv means of lead pipes from 

 12 to 18 inches in diameter, miles in length, and worked 

 under a head of 200 feet. It is true that the favourite 

 method of engineers before the nineteenth century, when 

 cast-iron pipes came into use. was to cross vallevs bv 

 bridge aqueducts, and this, apparently on the ground that 

 the materials of their pipes (either trunks of elm-trees 

 hollowed out, from which our word " trunk main " has 

 Hjrvived to us, or lcadl did not lend themselves to the 

 conveyance of large volumes of water as the ordinary 

 aqueduct did. The favourite system of supply in this 

 country to-day is undoubtedly by means of a gravitation 

 system, either from natural lakes like Loch Katrine cr 

 Thirlmere, or from artificial lakes — or, as they are called. 

 I impounding reservoirs." These reservoirs, by means of 

 a dam formerly formed of earth, with a core of impervious 

 puddled clay, but now more frequently of masonry, catch 

 and impound the water which falls upon the gathering 

 ground. Of course, it is desirable to avoid a gathering 

 ground which consists of cultivated land or upon which 

 there is any considerable population. The best gather- 

 ing ground is one composed of impervious rocks — for 

 porous strata steal too much water — and covered only 

 with mountain pasture or moorland. In many cases 



NO. 2l8l, VOL. 87] 



no objection is made to the existence of sheep upon 

 iii'' gathering ground; but Liverpool, in the case of its 

 Rivington works, has purchased the whole of the 

 gathering ground, and, after destroying and pulling down 

 many of the farms and buildings, has kept a great part of 

 the gathering ground free from sheep and let it to a 

 sporting tenant. The largest gathering ground in this 

 country dealt with by water works is the Birmingham 

 gathering ground, which will collect the water from 44,000 

 acres, while the Thirlmere scheme of the Manchester Cor- 

 poration has only a contributory area of 11,000 acres, 

 and the Vyrnwy works of Liverpool Corporation only 

 22,000 acres. 



Hundreds of dams have been built in this country to 

 collect the waters from gathering grounds in connection 

 with water supply to towns, or water supply to canals and 

 waterways. The wall which impounds the water at 

 Vyrnwy is 85 feet high. The Manchester Corporation, 

 which had to deal with a natural reservoir, constructed a 

 dam only SO feel in height, but the masonry embankment 

 at Caban Coch, the reservoir of the Birmingham Corpora- 

 tion, is 122 feet high above the bed of the river; and some 

 of the other dams of that great scheme, when complete, 

 will be 12S, 120, 101, and 98. These walls, of course, 

 have behind them immense quantities of water varying 

 from 8000 million gallons, in the case of Birmingham, 

 down to the very small number of gallons which run down 

 a mill goit. The tensile strain or tear of such a mass of 

 water as that at Caban Coch is enormous, and in that case 

 the work is strong enough to bear such a strain up to 

 12 tons per square foot. The Bouzay dam, near Epinal, in 

 Fiance, which was bad in design and faulty in con- 

 struction, gave way with the pressure of i\ tons to the 

 square foot. 



On January 13 of this year a dam of a reservoir con- 

 taining 250,000 cubic metres of water, which belonged to 

 the Huelva Copper and Sulphur Company, Spain, owing, 

 it is said, to a hidden spring under the masonry, gave 

 way, and eleven people were drowned. That is near to-day, 

 and affects us like a new wound. But even if none of is 

 have memories which go back to 1S40, tradition has told 

 us of the bursting of the Bradfield Reservoir, which 

 drowned the town of Sheffield, and put the country round 

 for a distance of 12 or 14 miles under water. In that 

 catastrophe 250 lives were lost, and property was destroyed 

 lo the extent of 327,000/. in value. The Holmfirth 

 Reservoir, which had an embankment 00 feet high and 

 150 yards long, after heavy rains burst in 1854, and 100 

 people were drowned in that night, and property valued at 

 600,000/. was destroyed. In most of these cases, however, 

 the calamity can be traced to the defective engineering 

 skill which Went to the construction, or subsequent care- 

 lessness in the maintenance. But many engineers would 

 tell you that they have sleepless nights when one of these 

 great cauldrons are filling with water for the first time — 

 and people in the valleys below may well hold their breath 

 until the stability of these great walls has been proved. 

 In the case of the Bradfield Reservoir, the burst reservoir 

 filled the Don Valley with a mad flood. In the town of 

 Sheffield the water rose to the height of the roofs of low 

 buildings. Dead cattle were carried down by the waters, 

 and in some cases deposited on house-tops, and as in the 

 days of Horace " fishes roosted in elms." 



In the case of spring waters, these are collected where 

 thev issue from the earth from their underground recesses in 

 protected tanks, and from these the water, which in many 

 rases has been sufficiently filtered by nature, is conveyed 

 to the clear-water tank, as in the case of surface water. 

 But when, as in the case of surface water, nature does 

 not produce a ready-made article, and the water is liable 

 to surface pollution, then filtration is a necessity, and, as 

 in manv other cases, in this connection our ancestors 

 were wiser than they knew. Indeed, experience is often 

 more valuable than science, and is universally the founda- 

 tion upon which all safe science is built. Sand filters have 

 been used in Britain since about 1S20. These filters are 

 tanks from 6 to 8 feet deep. Oyer the floor drain pipes 

 or channels lead to the outlet pipe, and over these we lay 

 a layer of broken stones and gravel. These stones are 

 laid to a depth of 2 or 3 feet, the larger stones being at 



