Burton: Geological Notes on Great Ayton. 369 
The general effect is a wall of basaltic rock, but there are 
numerous varying details. Several places were pointed out 
where the miners had come upon unexpected ‘troubles’ (a 
very expressive local term), where instead of the rock being 
continuous it was suddenly interrupted by what have generally 
been found to be wedge-shaped: masses of las shale cutting 
right across the Dyke in some instances, and in others running 
in the Dyke longitudinally, splitting it into two apparently 
separate walls. The explanation oftered was that when the 
intrusion occurred weak places in the lias strata allowed the 
liquid basalt to divide itself and follow two distinct courses 
upward, and that as the workings proceed downward the 
divided portions will probably be found to have one root. 
At one place it was pointed out the Dyke abruptly ended, 
and its continuation was found some distance away. This 
was considered to be only a variant of the transverse and 
longitudinal ‘ troubles’ and due to the same causes. 
Where the whole of the Dyke had been removed at the 
surface a huge, almost vertical slash had been cut into the 
hill, leaving the sides, chiefly composed of lias shales, clean 
and upstanding; and it was easy to observe the effect of the 
great lateral pressure which must have been experienced when 
the Dyke was formed. For a considerable distance (several 
yards) the cleavage, instead of being parallel to the bedding 
planes, was perpendicular thereto. Many of the shales also 
had been altered in character by the heat, and were known by 
the workmen as ‘ whiteback.’ 
Standing on the top of the Dyke, its course could easily 
be traced for several miles by its hog-back appearance. The 
hardness of the rock has no doubt preserved it from denudation 
more than has been the case with the lias shales on eithe1 
side. The rock is described as an Augite-andesite, and is 
believed to be part of the great Tertiary eruption. 
Another day was chiefly devoted to an examination of the 
the Estuarine beds of the Lower Oolite on the main escarpment, 
as well as on those near the top of Roseberry Topping. These 
latter are very remarkable, and have received a preliminary 
description by Mr. H. Hamshaw Thomas in a recent issue of 
The Naturalist. The evidence suggests that these plant beds 
are local so far as species are concerned, as quite a distinctive 
series of plants occur in profusion in one place and only 
very sparsely in another. On Roseberry Topping there is a 
bed of ‘paper coal’ composed of plant remains—largely 
Thinnfeldia rhomboidalis—and its abundance indicates a 
luxuriant vegetation, the decay of which was swept into 
shallow pools free from muddy intrusions. 
Cuttings for mining purposes through the middle lias were 
examined, and several minor faults were noticed, as well as 
1913 Oct. 1. 
