136 
[Hardra Limestone, Jew, or Sixth Sett] persistent. 
Sandstones and shales, thinning westward. 
[Top of the Mountain Limestone, already referred to as. 
thinning steadily toward the north-west, and passing into 
the Calciferous Sandstone Series towards the north and the 
north-east. | 
CONSTITUTION OF THE LIMESTONES. 
This varies to some extent; but in the main the organic 
constituents of the Mountain Limestone may be said to be 
Brachiopods, Mollusca, Foraminfera, some Polyzoa, and Corals. 
Of the corals not a single case anywhere can be demonstrated 
to be of the nature of a veef Coral stools there are, and in 
abundance, especially around Kendal; but of zee/s, or anything 
approaching reefs, there are none. Indeed it is doubtful if any 
case of a pre-tertiary coral reef has yet been made out. 
The constituents of the Yoredale Limestones are much the 
same as those of the limestones below, except that the percentage 
of mollusca entering into their composition is higher, and that 
Encrinites in these beds sometimes form nearly the entire organic 
constituents of masses of vast extent. Spirorbis also occurs on 
many horizons. 
In some of the higher limestones of the Yoredale Rocks sponge 
spicules occur in large numbers, whereby the rocks are often found 
to be largely replaced by silica. ‘That is to say, they are sz/iceous 
(not avenaceous). 
In the true Millstone Grit thin beds of more or less earthy 
limestone (which probably represent ironstones and coals towards 
the north-west) occur at many places in eastern and south-eastern 
Westmorland. 
In the Coal Measures proper (seen in Argill, near Brough) 
similar beds of impure, chemically-formed, limestone occur. In 
both this case and that of the Millstone Grit, these impure lime- 
stones may represent middle terms between coals towards the 
north-west, and thicker limestones of organic origin towards the 
south-east. It is far from unlikely, considering the nature of the 
