492 LOWER OOLITIC ROCKS OF ENGLAND : 
well as shells and small bits of limestone are apt to " blow " the 
bricks. 
Clays belonging to the Lower Estuarine Series have been dug for brick- 
making at Water Newton, Cottingham, Dene, and other places. At 
Stamford Baron, west of Burghley Park, clay has been used for the 
manufacture of terra-cotta. (See p. 203.) 
Fuller's Earth clay has been used for brick-making and burnt for 
ballast, at Powerstock. Bricks and tiles are made from it near Broad- 
windsor, Crewkerne, and Bradford Abbas. At High Cross Hill, between 
Haselbury and East Chinnock, red and mottled or yellowish tiles, drain- 
pipes and bricks are manufactured. Bricks, drain-pipes, and coarse 
earthenware were formerly made from the Fuller's Earth clay, west of 
Newbury, north-east of Mells : but the bricks, as I was informed by the 
Rev. George Horner, were of inferior quality. The clay is usually cal- 
careous and often contains racy nodules. In Gloucestershire it is generally 
too calcareous to be of service for brickmaking. 
In the Upper Estuarine Series, as remarked by Prof. Judd, the clays 
are admirably adapted for brick-making, for which purpose they are dug 
at Stamford, Great Oakley, "Water Newton, Wood Newton, between 
Stanion and Brigstock, and between Pilton and Luffenham. There are 
brickyards also at Buttocks Booth, south of Moulton, and north of Duston, 
near Northampton. In the lower part of the series at Little Bytham, 
clays are dug, from which are made bricks of singular hardness and 
durability (" clinker-bricks''). (See p. 418.) The Castor or Durobrivian 
Pottery, was made from. Estuarine clays, worked in Roman times in 
Normangate Field, Castor, west of Peterborough.* (See p. 202.) 
In reference to the Upper Estuarine Series, Prof. Judd states that " The 
clays contain just such a valuable admixture of siliceous matter in a finely 
divided state, as to adapt them for the manufacture, in some cases, of fire- 
bricks, and in others of tile- ware of peculiar h'ardness and soundness." 
At Wakerley, " the white clays at the base of this formation, are dug 
rather extensively by the well-known makers of terra-cotta, Messrs. 
Blashfield of Stamford. It is an excellent fire-clay, and is said often not 
to contain more than 15 per cent, of alumina ; it is, however, largely made 
up of finely divided quartz, with a considerable quantity of carbonate of 
lime, the latter sometimes in small oolitic grains, and at other times even 
occurring in the form of lumps of oolitic limestone, which are occa- 
sionally of considerable size. The muffle-tiles made of these Wakerley 
clays are said to withstand the severest heat for a longer time than the 
celebrated Stourbridge Clay. For pillars of terra-cotta, which are required 
to sustain a considerable weight, and at the same time to endure a con- 
siderable amount of heat (as, for instance, the columns employed in the 
construction of hospitals and other large buildings, which also serve as 
flues for conducting hot air), the Wakerley clays forms an excellent ' body.' 
For the finer classes of white and ornamental terra-cotta ware the 
Wakerley clays are of no use, as the roots and vegetable matters which 
abound in them (the masses being penetrated in every direction by the 
roots of trees) give the material made from them, when burnt, an un- 
pleasant yellowish tint." 
" The red ware at Stamford is usually made of a mixture of clays. 
These are as follows : The weathered Upper Lias of the valley of the 
Welland, which is of a dull brown colour, and full of selenite formed by 
the decomposition of nodules of iron pyrites ; the un weathered clays of the 
same formation, which are dug at greater depths at Stamford, and the 
similar Lias Clay from Manton tunnel ; and, lastly, the lighter Oxford 
Clay from the London Road, Peterborough, which is of a more sandy 
texture, and is found to prevent the other materials with which it is mixed 
from shrinking and cracking. These several materials are well crushed 
and ground together, and for the finer moulded work a proportion of 
* See E. T. Artis, The Durobrivse ; fol. Lend. 1828. 
