324 Prof. J. Buckmau on the Cornbrash of the 



water has soon become foul, and the whole contents of the tank, 

 both animal and vegetable, have rapidly suffered, and it has re- 

 quired some time before the water could be restored to its fonucr 

 healthy condition. 



In one of the numbers of the ' Zoologist ' of last year, I stated 

 that besides the Ulva, EnteromorphcB and Cladophorce, I had found 

 the Zostera marina a very useful plant for oxygenating the sea 

 water ; but this observation has reference only to the case of a 

 tank supplied with a ground where its roots will find a sufficiency 

 of food for its growth, as in a clear shingle or sand it soon de- 

 cays ; and it should be associated with such animals as delight 

 in a ground of this nature, as many of the Annelids, Crabs, bur- 

 rowing Shrimps, &c. There are several interesting observations 

 which have been made from time to time connected with this 

 subject, which I hope to lay before the natural-history world as 

 soon as I can find leisure time for the purpose. 



Apothecaries' Hall, Sept. 10, 1853. 



XXXI. — On the Cornbrash of the neighbourhood of Cirencester ^ 

 By James Buckman, F.L.S., F.G.S., Professor of Geology 

 lloyal Agricultural College*. 



The Cornbrash as it occurs in the neighbourhood of Cirencester, 

 though for the most part a very thin member of the Oolitic 

 series of rocks, yet presents us with many points for consider- 

 ation of great interest. 



In the counties of Gloucester and Wilts it is always found to 

 rest upon a thick bed of Forest marble clay, a section at Kemblc, 

 four miles from Cirencester, being as follows in descending 

 order: — 



1 . Cornbrash, an oolitic stone, with rough uneven fracture and ft. in. 



full of shells 8 



2. Blue clay without shells ) Fore^f 17 



Siliceous limestone ... j marble 6 



4. Bradford clay, very iossiliferous . 7 



5. Great Oolite 



The bed No. 1, which it is our object to describe in the fol- 

 lowing remarks, though of so slight thickness, is found to be the 

 substratum of large tracts of land, especially in the neighbour- 

 hood of Cirencester, Fairford, Cricklade, and IMalmsbury; in 

 each case presenting great and beneficial peculiarities of soil, 

 not only when compared with that upon its surrounding forest 

 marble, but also in comparison with other oolitic brashes; in- 

 deed, its name " Cornbrash " would appear to have been given 

 to it from the fact that its soil affords a brash or stony soil 

 * Read to the Cotteswold Naturalists' Club, Sept. 20, 185.3. 



