126 
THE LIAS MARLSTONE OF LEICESTERSHIRE. 
It is, however, found advantageous to mix a certain amount 
of the Northamptonshire stone with the Marlstone ore. 
The flux in general use is Derbyshire Limestone. Notwith¬ 
standing the large amount of water present, it is not usual to 
calcine the stone before putting it into the furnace. So far 
as the experiment has been at present tried, it is found that 
calcination, though it lessens the cost of manufacture, de¬ 
preciates the quality of the metal, the furnaces tending to work 
hotter and make a more siliceous iron, which is not so highly 
valued in the market. For the purpose of comparison, I 
append a couple of analyses of the Marlstone ores of Leicester¬ 
shire, the Cleveland district, and Oxfordshire, which may be 
taken as fairly representative of the quality of the stone in 
each instance. In reference to the Eastwell and Holwell ores, 
however, I wish to say that these analyses must not be taken 
as giving the relative richness of the ironstone at those two 
places, or, indeed, anything more than a rough idea of their 
general composition. The Marlstone ore varies so much in 
different beds, and in the same beds in short distances, that 
no two analyses, even in the same bed in the same quarry, 
would correspond. Hence, it is impossible from one or two 
analyses to determine the average percentage of this ironstone 
anywhere. 
When unweathered, the Leicestershire Marlstone is very 
similar in appearance and has a very similar composition to 
the Cleveland ironstone, being a fine grained oolitic rock of 
a bluish-green colour, and containing the iron in the state of 
a carbonate. It also belongs to the same geological horizon 
(Middle Liasj, and the two rocks may, therefore, be considered 
as approximately synchronous. In order to ascertain whether 
the percentage of iron in the unweathered marlstone of 
Leicestershire was such as to render it workable or otherwise, 
I have had two analyses of the Tilton stone made for me by 
Mr. G. F. Downar, analytical chemist, Bestwood, Notts. 
These analyses show that iron is present in the upper beds of 
the unweathered Marlstone Kock to the extent of from 25 to 
BO per cent.—a percentage quite equal to that of certain beds 
which have been profitably worked in Cleveland and else¬ 
where, and falling but little short of the average peicentage 
of the weathered marlstone ore of Leicestershire. It is not, 
however, to be supposed that it would pay to mine the 
unweatliered ironstone in a district where the weathered rock 
covers many square miles of country, is of about equal thickness, 
has a better percentage of iron, and, being a much softer 
stone, and lying at the surface of the ground, and at a good 
altitude too, can be much more economically worked. 
