1873.] D. WnUie— Purification of the Muddy Water of the Huyli. 175 



has also another of a darker brown, as shewn in the illustration of the 

 1 Ibis' for April 1865. 



Length about 26 inches ; wing 1975 ; tail 10 - 5 ; bill at front 2 in. ; 

 from gape 2 4 ; height at base 1*12 ; tarsus 325 ; mid toe and claw 3 in. ; 

 hind do. 2 25 ; bill dark horny, bluish grey at base ; cere apparently bright 

 yellow ; feet the same ; claws black. 



Hab. — Great Namaqua Land. 



2. Notes on the Certhiince of India. — By W. E. Beooks, C. E. 

 The author recognizes five species two of which are described as new. 

 The paper will appear in the forthcoming number of the Journal. 



3. On the Muddy Water of the Huyli during the rainy season with reference 



to its purification and to the Calcutta Water-supply . — By D. Waldie, 



Esq., F. C. S. 



Abstract. 



The author commenced by referring to a long series of experiments made 

 by him in 1868 and 1869 on the best kind of sand to be used in the filters 

 at Palta for the supply of water to Calcutta, and on the merits of a particu- 

 lar contrivance called Spencer's Regulating Cup proposed to be used in these 

 filters and alleged to be of great value in filtration. His enquiries resulted 

 in the condemnation of that cup as possessing no special advantage over 

 other plans for producing the same effect that it had, and in his recommend- 

 ing the employment of a finer sand than that used generally in England, 

 for the filtration of the Hugli water during the rainy season, during which 

 period it is attended with peculiar difficulty. It had been found of late, as 

 the demand for water increased, that the difficulty in supplying it had be- 

 come very serious. This difficulty had been treated as a failure of the plan 

 adopted, which had been condemned on account of its departure from the 

 principles of filtration recognised in England ; and it was proposed to remedy 

 this by reverting to practice founded on these principles and more especially 

 to the use of the Regulating cup. 



The author on the other hand maintained the correctness of his results 

 and conclusions, and contended that the proposals just mentioned were found- 

 ed upon principles fundamentally erroneous, because the real source of diffi- 

 culty lay in the peculiar quality of the river water during the rains, which 

 caused it to penetrate deep into the sand in a way which English waters 

 similarly treated did not do. He connected this peculiarity with the large 

 rainfall, limited to four or five months of the year, though he could not with 

 certainty explain the reason why it did so. Nevertheless he firmly adhered 

 to it as a fact. 



About the 1st of August last, an idea suggested itself to him of a cause 

 by which possibly the peculiarity might be accounted for, and a reference 



