260 PLASTIC CLAY FORMATION. 



The flints or pebbles composing the breccia (No. 3) are characterized 

 by their green and ferruginous crusts. 



This appearance is so peculiar, that it frequently serves to identify 

 the situations formerly occupied by the breccia, even where the stratum 

 itself has been broken up and destroyed. These pebbles are scattered over 

 the ploughed lands on the summits and slopes of the Downs, near Tar- 

 ring, Piddinghoe, Falmer, Stanmer, Bormer, and many other places in the 

 vicinity of Lewes. I have also detected them in the alluvium of the in- 

 to the formation of sulphate of alumine : this is decomposed by the chalk ; and aluminous earth, 

 selenite, and oxide of iron are the results." {Manual of Chemistry, 3 Vols. 8vo. 1821. Vol. 

 iii. p. 31'.i.) 



In the Annals of Philosophy for August, 1820, Mr. Cooper, of the Strand, gives a de- 

 scription of an aluminous chalybeate spring, situated on the coast between Newhaven and 

 Rottingdean. The precise situation of this spring is not mentioned, and my brother and my- 

 self have searched for it in vain. I can therefore add nothing to the following extract from 

 Mr, Cooper's letter : 



Description of an Aluminous Chalybeate Spring on the coast ofStissex, {from the Annals of 

 Philosophy, Aug. 1819. Ai-t. 11, No. 80, page 148.) 



" Dear Sir, 89, Strand, July, 1819. 



" I was requested to examine a bottle of water which was brought to me from the coast of 

 Sussex, between Newhaven and Rottingdean ; and although the quantity I had was small, 

 (being only about a wine quart) yet there was sufficient to ascertain its general nature and 

 characters, without regarding the quantities of its component parts. 



" The spring is situated, as I understand, about midway between Newhaven and Rotting- 

 dean, at an elevation of about 15 or 16 feet above the level of the sea at high water mark. It 

 issues from between the cliffs or fissures of the chalk in small streams, and these when united 

 pour forth fi-om 20 to 25 gallons in the hour. The chalk about the place is every where tinged 

 with an ochreous deposit. Its temperature as it issues is 65" Fahr. and remains constantly 

 the same, \^'hen I received it, there was a deposit of a brownish colour, which proved on ex- 

 amination to be oxide of iron. Its specific gravity, at the temperature of 60" Fahr. was 1-076: 

 it is slightly acidulous, changing the colour of litmus paper both before and after boiling, by 

 which operation it deposits a further portion of oxide of iron, and also a little lime. Reagents 

 show it to contain the following substances in solution: 



Oxide of iron. Lime, 



Alumina, Carbonic acid. 



Muriatic acid. Soda. 



Sulphuric acid, 

 •' This last substance I will not be quite certain of; but I expect shortly to be able to make 

 a more perfect analysis, and to give a better account of its situation, which is of some im- 

 portance, as I expect it is not far distant from the spot where the native alumina or subsulphate 

 is found. 



I am, &c. 



John Thomas Cooper." 

 " To Dr. Thompson." 



