820 REPORT—1890. 
occur, these formations are thicker than anywhere else in England. The thickness 
of the subdivisions of both Bunter and Keuper have been determined with great 
accuracy in recent years, and it is desirable to record the results. 
The following section shows the succession and relative thickness of each of 
the subdivisions as derived from railway sections and tunnels, borings for water 
and coal-pits :— 
Feet 
> { Red marl 5 . A - 400 
1d euuiaeet. | Keuper sandstone . : . 400 
Trias. | (peg: soft sandstone . - 550 
| Upper pebble-beds . z . 400 
ener Hyena: | Lower pebble-beds . “ - 600 
Lower soft sandstone . - 400 
2,750 
Excavations and borings have been in constant progress for many years, so that 
every bed in the Trias has been perforated, and in most horizons many times in suc- 
cession, and it is now possible tu tell exactly the strata to expect at any given depth 
when once those at the surface are ascertained. 
Microscopic Structure.—In the Trias, the sandstones forming the subdivisions 
present typical characters, though it often happens that some interstratified beds of 
a softer or harder nature occur, and differ trom those forming the rest of the 
strata. Ina series of beds of sandstone 2,350 feet in thickness, it is difficult to draw 
general conclusions of much value, but the microscopical examination of a great 
number of specimens from many horizons in the Trias around Liverpool shows that 
there are five normal types, although they run, more or less, into each other, as 
follows :-— 
1. Coarse-grained sandstone, composed of rounded and sub-angular grains of 
quartz, above ;},, of an inch in diameter. 
2, Fine-grained sandstone, composed of rounded and sub-angular grains of 
quartz, Zess than ;1, of an inch in diameter. 
3. Coarse-grained sandstone, containing a great number of large grains of quartz, 
st and <4 of an inch in diameter, like a minute conglomerate. 
4, Coarse-grained sandstone, composed of rounded, sub-angular, and crystallised 
grains of quartz—the crystallised faces having been deposited on the original grains 
after the sandstone was formed. 
5. Coarse-grained sandstone, or quartzite, originally formed of rounded and sub- 
angular grains which have been united, by the deposition of silica, into a hard rock 
after the formation of the sandstone. 
The lower soft sandstone is largely composed of the Nos. 1 and 3, and the upper 
soft sandstone of No. 2. Both the lower and upper pebble-beds are made up of No. 4, 
while the Keuper is the most variable, and consists of the Nos. 1 and 4, but all sub- 
ject to the occurrence of exceptional beds of sandstone. 
Triassic Pebbles.—The pebbles that occur in the Bunter formation are all found 
in the lower pebble-beds, and are usually less than an inch across, and it is very 
seldom that any reach the diameter of six inches. They consist of white-veined 
quartz, and quartzite varying in colour from white and grey to dark-red and brown. 
Nearly all are of a rounded or oval form, perfectly smooth, and must have come 
from a great distance, and most probably from the Cambrian and Silurian rocks of 
central England or Scotland. Next in frequency, though relatively few, are rough 
pebbles and angular fragments of coarse felspathic grit, sandstone, and chert, 
resembling beds in the Cefn-y-Fedw sandstone, Millstone Grit, and Coal Measures 
within 20 miles from Liverpool. These are generally found singly, but occur in 
brecciated beds on the coast of Cheshire, and the fragments are the largest at 
Hilbre Point at the mouth of the Dee. According to Professor T. G. Bonney, F.R.S., 
the quartzite pebbles resemble those found in Staffordshire, and it seems a question 
whether such a variety could have been derived from central England, or whether 
they did not probably come from the west of Scotland and travel along the easter 
side of the present North Channel into Lancashire and Cheshire. 
