466 PROFESSOR GEIKIE ON THE 
irregular lumps. They generally consist of some form of basalt (including all 
the fine varieties of dolerite) ; now and then, as at Ruddon Point, near Elie, they 
are amygdaloidal; and it may be observed among them, as among dykes in 
general, that where the amygdaloidal texture is developed, it is apt to occur 
most markedly in the central part of the vein, the amygdules running there in 
one or more lines parallel with the general trend of the mass. 
That the basalt of these veins and dykes was sometimes injected in an 
extremely liquid condition is shown by its frequently exceedingly close 
homogeneous texture. Within the neck on the shore to the west of Largo, — 
the basalt assumes in places an almost flinty texture, which here and there 
passes into a thin external varnish of tachylite. A farther indication of the 
liquidity of the original rock seems to be furnished by the great number of 
included extraneous fragments here and there to be observed in the basalt. 
But besides basalt other materials may more rarely be detected assuming ~ 
the form of dykes or veins within the necks. Thus, at the Largo neck just 
referred to, strings of an exceedingly horny quartz-felsite accompany the 
basalt,—a remarkable conjunction of acid and basic rock within the same 
volcanic chimney. To the east of Elie some dykes which stand out promi- 
nently on the beach consist of an extremely compact volcanic mudstone stuck 
full of worn twin crystals of orthoclase and pieces of hornblende and biotite. 
So like is this rock to one of the decomposing basalts, that its true fragmental 
nature may easily escape notice, and it might be classed confidently as a some- 
what decayed basalt. A considerable amount of a similar fine compact mud- 
stone is to be seen round the edges of some of the Elie vents. 
A columnar arrangement may often be observed among the basalt dykes. 
When the vein or dyke is vertical the columns of course seem piled in 
horizontal layers one above the other. The exposed side of the dyke then 
reveals a wall of rock, seemingly built up of hexagonal or polygonal, neatly 
fitting blocks of masonry, as may be seen on the Binn of Burntisland. An 
inclination of the dyke from the vertical throws up the columns to a pro- 
portional departure from the horizontal. Sometimes a beautiful fan-shaped 
erouping of the prisms has taken place. Of this structure the Rock and 
Spindle, near St Andrews, presents a familiar example. . Much more 
striking, however, though much less known, is the magnificent basalt mass of 
Kincraig, to the west of Elie, where the columns sweep from summit to base 
of the cliff, a height of fully 150 feet, like the Orgues d’Expailly, near Le Puy 
in Auvergne (fig. 10). ™ 
The veins or dykes seldom run far, and usually present a more or less a 
tortuous course. No better example of these characters can be cited than that 
of the veins on the south front of the Binn of Burntisland (fig. 14). These — 
vary in breadth from 5 or 6 feet to scarcely so many'inches. They bifurcate, anc ; 
