20 Rev. A Irving — Water Supply from the Bagahot Beds, etc. 



in these sands, we may, in the light of oui- present knowledge, pass 

 by without further notice. 



In an account of a series of analyses which is appended to Mr. 

 Eennie's Eeport, and signed William Thomas Brande, much stress 

 is laid upon what is prima facie a serious objection to the use of soft 

 water for dietetic purposes. It appears that the experimental evi- 

 dence goes to show that metallic lead is dissolved from the walls of 

 conduit-pipes much more readily by soft than by hard waters ; and 

 it is assumed, without any direct evidence being adduced, that this 

 is due to the mere fact of the ' softness ' of the water ; that is to say, 

 to its freedom from calcareous salts in solution. The experiments 

 appear however to have been tried with the native unpurified waters 

 of the Bagshot district ; we are therefore justified in asking whether 

 the solvent poM'er of these soft waters for lead is due, not to the mere 

 absence of calcareous salts, but to the presence of organic matter in 

 solution. The sources of such organic matter in waters drawn by 

 gravitation from the open surface of a country district are obvious 

 enough, as, for example, in the case of the water supplied to the 

 city of Manchester, which is drawn from the open moorlands of 

 North Derbyshire, or in the case of the water furnished to the town 

 of Birmingham, the greater part of which is collected by gravitation 

 into the vast basins which are to be seen in the parish of Shustoke. 

 "We must not overlook the fact that where calcareous salts are absent 

 in soft spring or well waters, there is so very often a quantity of 

 vegetable-matter present in solution, owing to the difference in the 

 conditions under which so many water-bearing siliceous sedimentary 

 strata have been deposited, as compared with the conditions under 

 which the calcareous sedimentary deposits were formed, that we 

 may fairly ask the question whether it is not entirely due to the 

 presence of the vegetable acids that * soft ' waters owe their supeiior 

 corrosive action on metallic lead. An affirmative reply to this 

 question is suggested by the fact that when crenic acid is present in 

 solution as an alkaline salt, it can be precipitated by acetate of lead 

 (Berzelius), the stronger acid going over to the stronger base, and 

 being itself replaced by the weaker acid. Further experimental 

 evidence however is required as to the direct action of the " humus 

 acids" upon metallic lead ; here it would be out of place to do more 

 than correct Mr. Brando's inference, by simply following his own 

 mode of testing.^ Granulated lead was exposed for twenty-four 

 hours in four test-tubes filled respectively with : — 



(1) Natural unpurified ' soft ' water from the Bagshot Sands ; 



(2) The same water as in (1) purified from vegetable pollution ; 



(3) Ordinary distilled water ; 



(4) Distilled water de-oxygenated by boiling for half an hour. 



The results observed were that a very decided turbidity was pro- 

 duced in sample No. 1, while all the other three i-etained the 

 perfect clearness of distilled water. It must be added that the 

 sample No. 1 was previously cleared of all suspended matter by 

 filtering, so that before the lead was placed in it, this sample was 

 1 pp. 15, 16 (ibid). 



