43*2 DR. S. F. HARMEU ON THE 



opportunity of inspecting and thus satisfied himself that it was 

 really composed of Polyzoa. 700 tons of this " moss " are said 

 to have been removed from the mains by an expensive and 

 laborious process ; but the subject was not investigated biologi- 

 cally, and I have been unable to ascertain anything more with 

 regard to the subsequent history of this case. 



At Paris {cf. Kemna, 05, p. 26) the Molluscan fauna of the 

 water-pipes was investigated by Locard, who recorded 44 species, 

 belonging to 13 genera. 



At Ypres, in Belgium (Kemna, 05, p. 63), a quantity of shells, 

 with masses of Polyzoa and innumerable Infusoria, could easily be 

 obtained by opening a hydrant in the streets. 



Mr. S. 0. Chapman, M.Inst.C.E., the Water Engineer to the 

 Boi'ough of Torquay, to whose kindness I am indebted for much 

 information on the subject of waterworks, is preparing a paper in 

 which he proposes to give an account of the troubles which have 

 been experienced in the district supplied by- the system under his 

 own charge, and of the result of the enquiries which he has made 

 of the Engineer's of other watei'works, at home and abroad. This 

 paper is expected to appear in the ' Transactions of the Institu- 

 tion of Water Engineers.' I believe I am right in saying that it 

 will contain valuable information tending to prove the correct- 

 ness of the view, which is held by nearly everyone who has studied 

 the subject, that the troubles which are caused by the occurrence 

 of a rich pipe-fauna can be got rid of by the introduction of an 

 efficient system of filtration. 



Enough has been said to show that the occurrence of conditions 

 favourable to the growth of Polyzoa and other organisms in the 

 pipes of a water-supply is not a matter to be treated lightly. A 

 study of the literature shows, moi-eover, that the Biology of 

 waterworks is a subject of great complexity and of very special 

 scientific interest. An excellent general account of the problems 

 involved has been given by \}r. A. Kemna (99, 05), who speaks 

 with special authority since, in addition to his scientific qualifica- 

 tions, he has had the advantage of being the Manager of an 

 important Water- Company which supplies the town of Antwerp. 

 As the subject is one which has not attracted miich attention in 

 Zoological liteiature, I may perhaps be excused for adding a few 

 remarks, based principally on Kemna's account (05), on the 

 subject of sand-filtration, which is so closely connected wdth the 

 practical side of the question. 



The introduction of sand-filters was due to James Simpson, 

 Engineer to the Chelsea Company, who gave evidence on the 

 subject before a Royal Commission on the Water-Supply of 

 London in 1827-1828, and before a Committee of the House 

 of Commons in 1828. Kemna comments (p. 109) on the fact 

 that although Simpson's views on the theory of sand-filtration 

 were not altogether sound, he nevertheless succeeded at his 

 first attempt in introducing a system which has not been 

 materially improved on since. 



