T. Mellard Reade—On the Lower Trias. 551 
1. Upper Permian. Red marls with thin-bedded fossiliferous limestones 
ae (Manchester). 
a 8 . & ( Red and variegated sandstone (Collyhurst, Manchester). 
Ba 9. == ) Reddish-brown and purple sandstones and marls with calcareous 
Ay 33 conglomerates and trappoid breccia (Central Counties). 
Previous to Prof. Hull’s investigations no subdivisions had been 
recognized in the Lower Trias or Bunter Sandstone, but that geologist, 
as the result of an extensive survey, considered that there were 
well-marked lithological differences in the beds which justified a 
classification into three horizons, namely,—1 Lower Mottled 
Sandstone; 2 Pebble Beds; 3 Upper Mottled Sandstone. It is 
upon this scheme that the Geological Survey maps were and have 
since been constructed. 
Considering the difficulties of the survey, much of the country 
being deeply drift-covered, the maps have fairly represented the 
geology of the areas surveyed, especially in those localities where 
the outcrop could be studied. It is in those places where the nature 
of the rocks could only be ascertained by boring that the weak points 
of a classification founded on lithological differences has naturally 
developed itself. 
In view of the numerous borings for water supply and for other 
purposes since made in Lancashire and Cheshire, certain modifica- 
tions have had to be made in the colouring of the maps showing 
the distribution of the subdivisions of the Bunter, and in some cases 
it is impossible to make the maps conform to nature and be logically 
consistent with the classification. Far be it from me to in any way 
seem to detract from the merits of the early attempts to conquer 
difficulties, especially where any classification is surrounded with 
pitfalls as it is in this case. It is a trying time for the geological 
surveyor when he is asked to predict the strata likely to be met 
with in a given bore-hole, yet this is what is demanded from a 
geological map; and if it occasionally errs, can we wonder ? 
Characteristics of the Triassic Sandstones. 
For the purposes of this paper it will not, however, be necessary 
to discuss these refinements of subdivision. I propose to treat 
principally of the Bunter Sandstone and its mode of origin, and 
with this object in view it will be sufficient to look upon it as a 
massive agglomeration of siliceous sandstones of varying fineness 
or coarseness of grain,.sometimes rounded, sometimes angular, more 
or less coloured by peroxide of iron, and often cemented together by 
secondary silica, or having crystalline growths thereon in optical 
continuity with the original quartz of the grain, even though the 
grain may have been previous to deposition well rounded by attrition 
of the surface. Within the interstices of the stone, and probably 
combined with the colouring matter, is a deposit of calcareous matter 
consisting of carbonate or sulphate of lime, sufficient, after continual 
circulation of water in the rock when brought about by artificial 
means, such as pumping, to impart a considerable amount of tem- 
porary and permanent hardness to the water. 
