BINXIE: MESOZOIC ROCKS OF THE NORTH-EAST COAST OF IRELAND. 65 
sheet within sheet. This appearance is due to weathering which has 
proceeded in stages, from the surface towards the interior. They are 
often of a rusty colour, coloured by the hydrated sesquioxide of iron. 
(3) The amorphous form is simply the ordinary form of basalt. 
The basalt occurs in ranges one above the other, each range 
lying on amygdaloidal beds, often exhibiting rude lines of lamination 
or stratification. 
Between these flows, lignite and iron ore occurs, the lignite repre- 
senting the old forests which sprang up again and again, only to be 
devastated by the next flow. There appears to be no rule connecting 
the mode in which each cousecutive lava flow is consolidated. First, 
one would be columnar, the next might be also columnar or spheroidal, 
or amorphous, and so on. It has been stated that this great volcanic 
outpouring was due to a gigantic fissure eruption, in which Mull 
participated, there has, however, not been one volcanic outburst, but 
many. As a rule the columns are either vertical or, in some cases 
where a dyke has pierced a previous outpouring, radiating at right 
angles to the dyke. In the amygdaloidal basalt many zeolites occur. 
The lignite, which occurs in the basalt is of little use as fuel ; 
the iron ore, however, is valuable, containing about 50 per cent, of 
oxide of iron, and a sufficient quantity of silicia to serve as a flux, in fact, 
it is sent to Glasgow to serve as a flux for other iron. It is due to 
the decomposition of the basalt, and occurs in horizontal sheets 
between the lava flows. It is now worked by a company at Lame, and 
exported in large quantities. 
The basalt forms the capping of the whole plateau described, 
except where it has been cut by the rivers. 
In some cases the foldings of the Mesozoic rocks are before, and 
in other cases after the laA^a flows. 
The age of the flows ii said to be miocene, as witnessed by the 
characters of the plant remains discovered and described in the lignite 
beds by Mr. Bailey in Ireland, and the Duke of Argyle in Mull. Mr. 
J. S. Gardner refers them to an earlier Tertiary age. How far the flows 
were confined to the miocene it is difficult to say, for they certainly 
occurred over a long period of time, for there are sometimes eight or 
nine flows superimposed, between each of which occurs a bed of 
