CHAP. XXXI 
AYRSHIRE , NITHSDALE AND ANNANDALE 
59 
That these are true lava-flows, and not intrusive sills, 
obvious from their general outward lithological aspect, 
some of them heing essentially sheets of slag and ^ ^ 
scoriae. Their upper surfaces may be found with a ^ -s 
fine indurated red sand wrapping round the scoriform js 
lumps and protuberances, and filling in the rents and 
interspaces, as in the case of the Old Red Sandstone 
lavas already referred to. As an example of these 
characteristics, I may cite the section represented in 
Fig. 200. At the bottom lies a red highly ferruginous 
and coarsely amygdaloidal basalt ( a ). Over it comes 
a volcanic conglomerate three feet thick, made up ol 
balls of vesicular lava like that below, wrapped in 
a brick -red sandy matrix (b). Lenticular bands of ^ 
sandstone without blocks occur in the conglomerate, -§ 
and others lie in hollows of its upper surface ( c ). This ^ 
intercalation of detrital material is followed by another ^ 
basic lava (d), about six feet thick, highly amygdaloidal 
in its lower and upper parts, more compact in the 
centre. The amygdales and joints are largely filled 
with calcite. The slaggy bottom has caught up and 
now encloses some of the red sand ot the deposit below. 
Another lava from three to six feet thick next appears 
{r), which is remarkable for its slaggy structure, and 
is so decomposed that it crumbles away. Like the 
others it is dull-red and ferruginous and full ot calcite. 
It must have been at the time of its outflow a sheet 
of rough slag that cracked into open fissures, lhat “S 
it was poured out under water is again shown in the ^ 
same interesting way just referred to, by the red sand 
which has been washed into the interspaces between 
the clinkers and has filled up the fissures, in which 
it is stratified horizontally between the walls. Above 
this band, and perhaps passing into it as its slaggy 
base, lies another more compact lava (/) like the lower ^ 
sheets. If 
Throughout the series of lavas, as indicated in 
the foregoing section, traces of the pauses that elapsed 
between the separate outflows may be seen in the 
form either of layers of red sandstone or of tuft and 
volcanic breccia. Here and there, under the platform 
of bedded lavas, the brick -red sandstone is full of 
fragments of slag and fine volcanic dust. But the ^ 
most abundant accumulation of such detritus is to ^ 
be seen at the top of the volcanic series, where it 
contains the records of the closing phases of eruption. 
is sufficiently 
Thick beds of 
