288 LIAS OF ENGLAND AND WALES : 
CHAPTER XI. 
ECONOMIC GEOLOGY. 
and Cement. 
THE Lower Lias limestones have long been celebrated for their 
hydraulic cement and Blue Lias lime. 
Many of the layers or nodules of stone furnish naturally the 
ingredients required for " water-linie " or hydraulic cement, and 
they are known as cement-stones or cement-beds : thus the pro- 
ducts are spoken of as Natural cements, in distinction from the 
Artificial Portland cement, made often by mixing materials 
obtained from different strata and localities. 
Great part, however, of the cement made from the Lower Lias 
is produced by a mixture of a number of layers of stone and 
sbale or clay ; a plan necessary on account of the limited quan- 
tities of the good cement-beds, and necessary also in order to 
ensure uniformity in the products. Not only are the layers 
different in character, but e:ich individual layer is liable to varia- 
tion. Some of the best cement-beds are dark shaly limestones, 
others are nodular masses of argillaceous limestone. Layers that 
contain pyrites must be rejected. 
At the base of the Lower Lias generally throughout England, 
there are alternate bands of more or less argillaceous limestone 
and shale or clay, but the quality of the strata and the thickness 
of the beds adapted for the preparation of lime and cement, vary 
considerably. In some localities the limestone-bands are com- 
paratively few, in other cases we have a mass of limestones and 
shales attaining a thickness of 200 feet. Beds on different strati- 
graphical horizons are worked in different localities, though in all 
cases, as regards the Lower Lias, they belong to the lower zones 
of Ammonites planorMs, A. anyulatus, and A. Bucklandi. 
So called '* Blue Lias Lime " is made from strata of Inferior 
Oolite age at Kirton Lindsey, and from other formations ; but in 
such cases the use of this name for trade-purposes is unfortunate, 
although the lime produced may be of first-rate quality. 
True Blue Lias lime and cement are prepared from material 
obtained at Aberthaw, Bridgend, Stormy Cement Works near 
Bridgend, Lliswerry, Watchet, Dunball near Bridgwater, Lang- 
port, Lyme Regis, Pylle. Shepton Mallet, Weston near Bath, 
Wilmcote, Harbury, Stockton, Rugby, Barrow-on-Soar, Evington, 
Barnstone, Granby, Elton, Gotham, and Codclington ; and at 
some other localities mentioned previously. 
At several of these localities the lime has been long celebrated. 
J. Woodward, in 1729, speaks of Ammonites "Found in a 
