438 On the Causes of the Colour 



hence, unless it is to be found in situ at a moderate depth 

 below this clay ; which is, I think, not very improbable, con- 

 sidering that these portions of soft chalk could not have been 

 drifted a long distance without being dissipated by the trans- 

 port. I only notice this circumstance in support of the con- 

 tinuance of the chalk strata to our western coast, where it has 

 been perforated in boring for water; and [in the idea] that 

 its basin is shallower, under this lacustrine deposit, than in 

 many other places ; as many of the wells in this neighbour- 

 hood are 50 ft. and 60 ft. deep, without getting through our 

 gravel beds, although my own well, only 37 ft. deep, and 

 within a mile and a half of Copford brickfield, penetrates the 

 London clay about 2 ft. 



Although the shells of these strata are in a broken state, still, 

 by an attentive observation, we can trace the forms of several 

 genera; the Planorbis, Paludina, Valvata, and Cyclas; all of 

 which are abundantly found living in the pools and ditches in 

 this neighbourhood. 



Admitting the ox to which the horn above noticed was 

 once attached, to have belonged to one of our lost species of 

 Mammalia, its being found associated with recent Testacea 

 is an illustration of Professor Lyell's observations on this in- 

 teresting subject, in his most excellent work, the Principles 

 of Geology, vol. iii., p. 140. 



Stanway, near Colchester, May 5. 1834. 



Art. IX. Enquiries on the Causes of the Colour of the Water of 

 the Rhine ; by J. R. : xuith Remarks, in Contribution to an 

 Answer; by the Rev. W. B. Clarke, A.M. F.G.S. 



I DO not think the causes of the colour of transparent water 

 have been sufficiently ascertained. I do not mean that effect of 

 colour which is simply optical, as the colour of the sea, which 

 is regulated by the sky above or the state of the atmosphere, 

 but I mean the settled colour of transparent water, which has, 

 when analysed, been found pure. Now, copper will tinge 

 water green, and that very strongly ; but water thus impreg- 

 nated will not be transparent, and will deposit the copper it 

 holds in solution upon any piece of iron which may be thrown 

 into it. There is a lake in a defile on the north-west flank of 

 Snowdon, which is supplied by a stream which previously 

 passes over several veins of copper : this lake is, of course, of 

 a bright verdigrise green, but it is not transparent. Now, the 

 colouring effect, of which I speak, is well seen in the waters 

 of the Rhone and Rhine. The former of these rivers, when 



