113 



cost of the coals ; and if we also softened the same quantity with 

 carbonate of soda (washing soda) and again a similar quantity with 

 soap and then compared the cost we should find : — 



£ s. d. 

 1 cwt. of lime costs, say . . ..008 

 4f cwt. carbonate of soda . . . . 2 17 9 

 20J cwt. of soap 47 1 8 



(The above calculation is given in one of the Reports of the 

 Royal Commission on water supply). 



We may put the matter in another way however. If we 

 suppose that three millions of gallons of the total weekly supply of 

 water is used in Dover for washing purposes, the value of the soap 

 wasted in producing useless curd with it is over £510, which is 

 about four-pence 2}er head of the ])opidation. 



There are certain drawbacks to the use of very soft water. It 

 is said to produce " rickets " in children owing to insufficiency of 

 lime for bone formation. The gravest defect, however, is that soft 

 water attacks leaden pipes, whence cases of lead poisoning are by 

 no means rare where the water is very soft. 



There is one part of water analysis wliich I have not touched 

 upon, but which is now attracting great attention. That is the 

 bacteriological examination of water. A specimen of water might 

 pass a splendid chemical examination, and yet be a deadly draught, 

 owing to its containing bacteria which almost entirely escape 

 chemical tests. But where there is an efficient system of filtration 

 through sand, especially when the filtering beds have been so long 

 in use as to become covered with a slime of bacteria there is little 

 danger. It is a curious fact, but it certainly seems proved to be the 

 case, that the older and more slimy the filter beds are, the more free 

 from bacteria is the water passing through them. In fact, in a case 

 brought before the recent Royal Commission, sand filtration had 

 reduced the bacteria present in a sample of water, from one- 

 quarter of a million per cubic centimetre, to something like four 

 thousand, which is a reduction of ninety-eight per cent. Still, 

 however, four thousand bacteria per cubic centimetre will seem to 

 many of us more than we care to imbibe, for it means over one 

 million in a tumblerful, but we shall doubtless accept the inevitable 

 when we remember that there are over nine thousand million 

 bacteria in every pound of fresh butter ; thirteen hundred millions 

 in every pint of milk ; and three thousand millions in every pound 

 of sausages. Here, again, " what can't be cured must be endured." 



Dr. Percy Frankland has recently drawn attention to a remark- 

 able case where the water supply was chemically fairly pure, and 

 yet most disastrous efi'ects followed its use, whilst the same water, 



