290 LIAS OF ENGLAND AND WALES : 
crushed, ground in a mill, and passed through fine sieves. It is then ready to 
be put into barrels or sacks for delivery. 
In some instances "Portland cement" is manufactured from specially 
selected Lias stone ; and this is said to set more quickly than the ordinary 
Blue Lias cement. Particular varieties are also supplied to the trade under the 
names of Roman, Bath, and Lias cements, some setting more rapidly than 
others, and possessing different degrees of tenacity. 
The essential constituents in cement are : Lime 45 to (55 per cent., clay 20 
to 30 per cent., and oxide of iron 3 to 14 per cent. In the preparation of the 
cement, it is necessary in some cases to add a certain amount of oxide of iron, 
when the stone and shale are deficient in it. 
The hydraulic powers of the cement are dependent on the amount of 
soluble silica ; a double silicate of lime and alumina being formed during the 
preparation of the material. 
Selenitic cement is made in some places. This is formed from a mixture of 
calcined gypsum, sand, and hydraulic lime. It is used for mortar, plastering 
on lath-work, stucco and concrete.* 
Artificial Stone. 
The Blue Lias Cement is employed in the manufacture of 
some of the artificial paving-slabs, sinks, and troughs. Thus 
chips of Mount Sorrel stone are embedded in " portland cement " 
and shaped in moulds. Afterwards, when solidified, they are 
steeped in a " silica solution," formed of silicate of soda, and in 
this the slabs remain immersed for seven or eight weeks. This is 
done at Barrow-on-Soar for the manufacture of Granolithic pave- 
ment. " Victoria Stone " is similarly made from Groby rock. 
At Rugby, concrete is formed with cement and chips from stone- 
quarries, and fashioned into window-sills, coping-stones, paving- 
slabs, &c. The silica solution is of great service in filling up all 
the interstitial spaces in the concrete. 
REFERENCES TO TABLES OF ANALYSES. 
A. Analysis by Mr. John Spiller (1870). Communicated by Mr. Wm. 
Porter. 
B. Analysis by Mr. Henry T. Jones, F.I.C. (1888). Communicated by Mr. 
Wm. Porter. 
C. Analysis by Messrs. Holland and Phillips (1883). Communicated by 
Messrs. John Davies and Company. 
D. P. Analyses by Mr. W. Harry Stanger (1888). Communicated by 
Messrs. Greaves, Bull, and Lakin. 
E. Analysis by Mr. Charles Tookey (1858). 
F. Communicated by Messrs. Chas. Nelson and Company. 
G. H. Communicated by Mr. C. Hall. 
I. Communicated by Messrs. John Ellis and Sons. 
J. Analysis by Mr. J. Bernard Dyer, F.C.S. 
K. R. Communicated by Mr. H. Parry. 
L. Analysis by Mr. H. Faija, Communicated by the Somerset Lime and 
Cement Company. 
M. Analysis published by Mr. H. Reid. 
N. Analysis by Mr. H. Faija (1885). Communicated to Mr. A. Strahan, 
by Messrs. John Davies and Company. 
O. Analysis 'published by Mr. H. Reid, Manufacture of Portland Cement, 
1877, p. 56 ; see also R. Phillips, Ann. Phil. ser. 2, vol. viii., 1824, 
p. 72 ; and A. Voelcker, Journ. Bath and W. of Eng. Soc., ser. 2, 
vol. vi., p. 228. 
P. Analysis published by Mr. H. Reid. 
* See also John Grant, Proc. Inst. C.E., vol. Ixii. p. 98 ; and Notes on Building 
Construction, Part III., ed. 2 (Itivingtons), 1889, p. 145. 
