234 



NATURE 



[August 17, 191 1 



the bottom ol the tanks, and the smaller bearing the 

 . feel of sand, which was supposed to be the filtering and 

 purifying medium. I"he water is allowed to percolati 



downwards at a certain slew rate, and the effect is to 

 removi mechanical!) certain matters in suspension. For 

 many years our chemical experts saw little or no value 

 in sand filtration, because in chemical analyses they found 

 little or no difference between the filtered water and 

 the unfiltered raw water. But it was left to bacterio- 

 logists to find the real significance of sand filtra- 

 tion. We know now that after use a jelly-like deposit 

 is formed on the top of the sand, and that that 

 film has prevented the water from getting through the 

 filters at the ordinary vertical rate of 4 to 6 inches an 

 hour, or about 2; million gallons a day per acre of sand. 

 One ingenious engineer had the jelly scraped off the 

 surface of hi* filter, and the water flowed more freely 

 certainly, but there were within a few hours urgent tele- 

 phonic messages from the bacteriological department 

 announcing the arrival of thousands of bacillus coli, and 

 that the water supplied by that company was not fit to 

 drink. The fact is that it is the organic slime which is 

 formed on the top of the sand, and which the sand is 

 only useful in supporting, that is the effective agent in 

 filtering the water, for the organic slime destroys the 

 micro-organisms which are in impure water. It is in this 

 respect that our ancestors, in using their sand filters, were 

 wiser than they knew. 



While the micro-organisms which cause cholera, 

 typhoid, and tubercle are so rapidly conveyed to us by 

 means of water, and then exercise their fateful activities, 

 which bring us disease and death, there are beneficent 

 bacteria which "come to succour us who succour want," 

 and these are applied as a bastion or a defence against 

 our enemies by means of the at one time despised sand 

 filter. I think it was Napoleon who said that a wise 

 general should not fight too often with the same enemy, 

 for the enemy was apt to learn too much from his implac- 

 able foe. We have fought often with the bacillus of 

 cholera and typhoid, and have learned of our battles. 

 Nothing could be more tragic in the way of instruction 

 than what took place at Hamburg and Altona in 1892. 

 Both Hamburg and Altona are dependent for their water 

 supply on the Elbe, but the intake for the Hamburg supply 

 is above the town ; the intake for the Altona supply is 

 below Hamburg, at a place below the point where the 

 sewage of that town, with its Soo.ooo inhabitants, is dis- 

 charged into the river. The Hamburg supply had, there- 

 fore, a great initial advantage over that of its neighbour- 

 ing town. But the cholera epidemic scourged Hamburg, 

 and the Angel of Death passed very lightly over Altona. 

 At Hamburg the deaths from cholera amounted to 1250 

 in 100,000, and at Altona to only 221 per 100,000 ol tin 

 population. Where the division between the two towns 

 was only the imaginary line down the centre of a street, 

 and the houses on one side of the street, being in Ham- 

 burg, were supplied with the above-town water, and the 

 houses on the other side were supplied by the below-town 

 water, the cholera visited with fatal results the houses on 

 the Hamburg side, while those on the Altona side were 

 free from the disease in this new Passover. 



These haggard statistics are to be accounted for only by 

 the fai t that the foul sewage-polluted water of the I'll" 

 which was supplied to Altona was carefully filtered, while 

 tli mparatively pure water taken above Hamburg bli- 

 the supply of that town was not. Altona had the protec- 

 tion of the micro-organisms in its sand filters. Hamburg 

 had no such protection, and suffered accordingly. 



A similar experience in relation to another water-borne 

 disease- typhoid — has been put on record by the Massa- 

 chusetts Board of Health. There in twenty vears. from 

 1856 to 1S76. the death-rate from typhoid in thai State 

 was 8-6 per 10,000 of population: in the years between 

 1X70 and 1895, when private wells had been given up and 

 a publii supplj of filtered water substituted, the death- 

 rate was only 4-1 pel to, 000, and between 1896 an. I iSno 

 tli'- death-rate went down to 2.6 per 10,000. Hie Stati 

 reporl says : — " The death-rate from typhoid fevei 

 has generally fallen as the percentage of the population 

 supplied with public water has risen, for th.' reason that 



the majority of the deaths from this di ccurred 



among communities and portions of communities not sup- 

 plied with public water." 



But an examination of our own I hames water at 

 Hampton showed there were 11144 micro-organisms in 

 twenty drops „t water, and the water, after pass- 

 ing through the sand filters, was found to contain only 

 thirteen such organisms in the same number of drops. 

 The discovery of the 1644 germs was at the time so 

 startling that the shares of one of the water companies 

 dropped in value ; and I think these 1600 did valiant duty 

 in the arbitration which had to determine the value of the 

 company's undertakings when they were being transferred 

 to the Water Board. 



But notwithstanding these startling vindications of sand 

 filters, the great town of Chicago takes its water from 

 Lake Michigan, which receives the untreated sewage ol 

 various towns having in the aggregate a population of 

 more than two million people, and has not thought it 

 necessary to subject its water to any preliminary purifica- 

 tion before distribution. That town has, however, with 

 curious inconsistency, diverted its own sewage from the 

 lake, but it has undertaken that sanitary improvement 

 only in connection with the commercial undertaking ol 

 the drainage and ship canal. 



We know that one of the riddles of the politico-economic 

 platform is, " What is raw material, and what is a manu- 

 factured article?" But we have seen sufficient to see 

 that " raw water " is quite a rare commodity, and that 

 most of our waters are manufactured artii les. Even 

 eastern countries like China and India have long 

 " doctored " water with alum to get rid of clay by coagu- 

 lation. But in this country not only do we get rid of the 

 turpidity of water by sedimentation, but we purge the 

 waters of micro-organisms, including pathogenic germs, by 

 storing in large reservoirs, as well as by filtration. Very 

 hard waters, waters containing lime and magnesia, are 

 treated and softened by what is called Clarke's process. 

 Everyone knows that chalk waters fur boilers and kettles, 

 and that the bicarbonate of lime is precipitated by boil- 

 ing; but Clarke's process consists of a chemical method 

 which expels chalk by chalk, and is an ingenious applica- 

 tion of science to the practical purpose of softening water 

 which lengthens the life of boilers and saves soap. But, 

 again, water may be too soft. Hill waters are sometimes 

 too soft to be palatable. Water at Keswick is under half 

 a degree of hardness ; Loch Katrine water, 1 degree ; 

 Thames and New River water is about 14 degrees. 



But it is found that distilled water, or soft lake or river 

 water, acts with extreme rapidity upon lead, and many 

 cases of lead poisoning have occurred in consequence of 

 persons drinking waters which have been in contact with 

 the lead of which distributing pipes are, for the most 

 part, constructed. It has been said that sand filters re- 

 move the lead; but at present it is the rule t.i treat, or 

 " doctor," these very soft waters, as is done at Sheffield, 

 where, to overcome this difficulty, from half to (rarely) 

 three grains ..I powdered chalk is added to each gallon of 

 water with excellent results. It has been found, too, that 

 loam or clay remove by merely carrying down organic or 

 inorganic impurities from water; and it is certain that 

 the precipitation of lime which takes place in Clarke s 

 process has some effect in the same direction, although, 

 from experiments made by Dr. Percy Frankland in con- 

 nection with the Cambridge Water Bill of iqio, it does 

 not seem to he a thoroughly effective method of purifica- 

 tion. In connection with that Bill, a suggestion was made 

 that suspicious waters- waters drawn from wells in the 

 chalk in close proximity to certain villages — could be made 

 perfectly safe by the chlorination of water; and it was 

 stated that the ozone process which has been adopted in 

 relation to certain waters forming part of the supply to 

 Paris is also a useful and protective process in cases where 

 waters are liable to organic pollution, and in which the 

 danger-signal of bacillus coli is found. These instances 

 are sufficient to show that water, to be potable, must pass 



through the hands, not only of the engi r with his 



filter and storage, but also through the hands of the 

 chemist and bacteriologist- in fact, water, unlike the poet, 

 is made, not born. 



:i8i, vol. 87] 



