Rev. A. Irving — Water Supply from the Bagnhot Bech, etc. 21 



as clear to the eye as the other three were. It is better to reserve 

 further discussion of this subject for another place : so far as the 

 experimental evidence here cited goes, it would appear that Mr. 

 Brande's fallacy (and that of those who have followed him) consisted 

 in overlooking the action of vegetable acids present in solution in 

 the samples which he examined from the Bagshot district. 



" Many of those waters which act upon lead." says Mr. Brande at 

 p. 20, " are also apt to derive contamination from iron, when con- 

 ducted through pipes of that metal." This is notoriously the case 

 with the Bagshot waters, as I pointed out in my previous paper; 

 and, in the light of later experience, I do not hesitate to aflSrm that 

 by far the greater portion of the iron contained in the ochreous pre- 

 cipitate, which these natural waters, after passing through iron pipes, 

 deposit on exposure to the air, is taken up in solution by the direct 

 action of the vegetable acids in the water upon the metal of the 

 pipes. This fact, coupled with the generalization of Mr. Brande 

 quoted above, aifords indirect but strong support to the theory, that 

 it is only to the frequent presence of the ' humus-acids ' in soft 

 natural waters that we can fairly attribute danger arising from the 

 superior corrosive action of ' soft ' waters upon lead. This however 

 fails at once as an objection to the use of such waters for dietetic 

 purposes, when we come to know that such vegetable pollution of 

 water may be easily removed before the water is led through metal 

 pipes. 



In my former paper I pointed out that we seldom or never see in 

 returns by professional analysts any note as to i\iQ nature of vegetable 

 pollution of water, though the presence of such matter is frequently 

 indicated. It would be well if in all cases the presence or absence 

 of vegetable pollution were stated, the term ' organic matter ' not 

 being sufficiently definite. Under cover of the latter term I have 

 known a writer covertly suggest the befoulment of a certain water 

 obtained from peaty sources with something of a far more serious 

 nature than vegetable matter, when he knew all the time the real 

 facts of the case. It would also be well if regard were had, in all 

 cases of analysis of supposed potable waters, to the time which elapses 

 between the collection of a sample and its systematic examination. 

 All statements then as to presence or absence of odour, ' flocculent 

 matter' deposited, etc., would admit of a more definite interpretation 

 than they do unaccompanied by such data ; since; however well a 

 bottle may be stopped, it is quite impossible to have filled it with 

 water, without the water absorbing a certain amount of free oxygen 

 from the air, if it is not already fully oxygenated. This remark 

 applies of course in an especial manner to water drawn from deep 

 wells. In illustration of this point I may refer to a case of a well, 

 the water of which is certified by a professional analyst to be " very 

 free from organic pollution"; yet this water fresh from the well 

 has the taste and smell peculiar to vegetable pollution in a high 

 degree, gives an ochreous deposit after being passed through iron 

 pipes, and is found on examination to contain a very considerable 

 quantity of the humus-acids in solution. 



