THE PORTLAND BUILDING STONE. 
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comparatively free from joints. The quarries present per- 
pendicular cut faces, retaining the marks of the instruments 
used for the extraction of the stone. Blocks of considerable 
size are extracted, and easily cut while soft into any required 
pattern ; the colour, however, is not very good in the fresh 
state, being a yellowish- grey, but soon tones down on exposure 
to the weather into a nondescript ‘ stone ’ colour ; and in this 
respect, therefore, the stone is inferior to the production of the 
island. In some quarries the goodness of the stone is interfered 
with, though its interest for geologists is increased by a band of 
chalcedony, which has congregated sometimes round Trigonias 
and sometimes round corals. The latter are very beautiful 
objects, of which specimens are scattered through many collec- 
tions ; but they are now apparently utterly exhausted, and no 
more are to be obtained. These bands have doubtless, like 
the flints, been formed by infiltration through the surrounding 
mass, but here lie in bands instead of irregular nodules, because 
of the more regular stratification of the rock in which they 
occur. Mentioning these, however, it may be added that over- 
lying these very building stones and forming their ‘ bearing ’ 
is a mass of white, calcareous, soft rock with siliceous nodules, 
so exactly like the ordinary chalk and flint, that they might 
easily deceive a casual observer, and actually differing in 
scarcely anything but their fossils, and consequently their age. 
But in this district there is one great quarry in which a 
higher stone is worked ; this lies above the chalky rocks just 
mentioned, and thus is separated by them from the lower free- 
stone. This higher stone is a very beautiful one; it has a 
brilliant white colour, and rings like a bell beneath a blow of 
the hammer ; it is very free, very soft when first extracted, 
and large blocks may be obtained; moreover, to judge from 
the colour of the cast-out refuse, it does not easily discolour. 
It would seem, then, to have everything to recommend it ; 
it is, however, somewhat coarse in the grain, and holes occur 
in it here and there ; and, as far as can be seen, it must be 
very limited in quantity. Its high position in the series, and 
the succession of the overlying Purbecks, point it out to be on 
the same horizon as the true Portland Stone, so that the 
circumstances which favoured the production of a valuable 
quality may have here been repeated. The celebrated * dirt 
bed/ with trees, of the Isle of Purbeck, is here repeated ; the 
vegetable soil, the stems of the trees, but not as yet the roots. 
The only remaining area in which Portland Stone is worked 
is the typical district which extends from Portland as far as 
Swanage on the east and Upway on the north. The upper 
surface of the Island of Portland may almost be described 
as one great quarry, so riddled is it everywhere by excava- 
NEW SERIES, VOL. IV. NO. XV. P 
