CHAl’. XXVII 
LAVA-STREAMS AND TUFFS OF THE PUYS 
445 
conies a bed of limestone (11) 1 5 feet thick, the lower layers of which are 
made ii}) of a dense growth of tlie thiii-stenimed coral Lithostrotion irregularc. 
The next stratum is a band of dark shale (C) 
about two feet thick, followed by about the same 
tliickness of an impure limestone with shale seams 
(1)). The conditions for coral and crinoid growth 
were evidently not favourable, for this argilla- 
ceous limestone was eventually arrested first by 
the deposit of a dark mud, now to he seen in 
the form of three or four inches of a black pyri- 
tous shale (E), and next by the inroad of a large 
quantity of dark sandy mud and drift vegetation, 
which has been preserved as a sandy shale (E), 
containing Calamites, Proclucti, ganoid scales and 
other traces of the life of the time. Einally, 
a great sheet of lava, represented by the upper- 
most amygdaloid (G), overspread the area', and 
sealed up these records of Palaeozoic history.^ 
Among the phenomena associated with the _ ^ „ 
^ ^ . . Fig. 15b. — Seotion iii Wardlaw 
Carboniferous volcanoes mention may, m con- Quarry, Uniitiigowsiure. 
elusion, be made of the evidence for the former 
existence of thermal springs and saline sublimations or incrustations. 
Among the plateau-tuffs of North P)erwick, as has been already pointed out (p. 
390), a foetid limestone has been quarried, which bears indications of having 
been deposited by springs, probablj" in connection with the volcanic action 
of the district; 'The lower limestones of Bathgate furnish abundant lamime 
of silica, interleaved with calcareous matter, the whole probably due to the 
action of siliceous and calcareous springs connected with the active puys of 
that district. Some portions of the limestone are full of cellular spaces, 
lined with chalcedony.'^ A saline water has been met with among the 
volcanic rocks to the west of Linlithgow, in a bore which was sunk to a 
depth of 348 feet in these rocks without reaching their bottom. 'The 
water that rose from the bore-hole was found to contain as much as 135 
grains of chloride of sodium in the gallon. It is not improbable that this 
salt was originally produced by incrustations on the Carboniferous lavas 
immediately after their eruption, as has happened so often in recent times 
at Vesuvius, and that it was then buried under succeeding showers of tufl' 
and streams of lava.'* 
SvMequent Bidocation of Bedded Lavas and Tuffs. — As the interstratified 
volcanic materials were laid down in sheets at the surface, they necessarily 
behave like the ordinary sedimentary strata, and have undergone with them 
the various curvatures and fractures which have occurred since Carbon- 
' liml. Sun. Mevi: “ Geology of Edinburgli,” p. 58. 
■- Ihicl. p. 49, ct scq. 
■' Proe. Roy. Soc. Ediii. vol. ix. p. 367. Besides chloride of sodium the water contained also 
chlorides of calcinm, magnesium and potassium, carbonates of lime and magnesia, .sulphate of 
lime, and other ingredients in minute proportions. 
. / ,• f - 7 ^'?^'^' ' 
