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TII.—On the Lower Silurian Lavas of Eycott Hill, Cumberland 
By J. Currron Warp, Assoc. R.S.M., F.G.S., of Her Majesty's 
Geological Survey. 
(Read before the Royau Microscoricau Society, April 4, 1877.) 
PLaTE CLXXXYVII. 
CONTENTS. 
Introduction. 
1. Examination in the Field. 
2. Microscopical Examination. 
3. Chemical Examination. 
Introduction. 
Tue series of lavas which I propose to describe belong to the 
northern extension of the volcanic series of Borrowdale, Cumber- 
land. This series has been treated of in my memoir on the 
Keswick district, and touched upon in various papers communi- 
cated to the Geological Society. My object in the present paper 
is to point out the value of microscopic research to the field- 
geologist both from a practical and a theoretic point of view, and 
at the same time to illustrate somewhat in detail the microscopic 
structure of a fine succession of ancient Silurian lava-flows. 
Eycott Hill lies in the north-eastern part of the Lake district, 
just outside the range of the mountains, and a mile and a half 
north of Troutbeck station on the line of railway from Penrith to 
Keswick. The hill is often locally known by the name of Berrier 
Nittles, and its highest point, through which the section (Plate 
CLXXXII.) runs, is 1131 feet above the sea. 
1. Hxamination in the Field. 
The horizontal section, on the scale of six inches to a mile, 
Plate CLXXXIL., shows the series now to be described, dipping at 
a tolerably regular angle of from 35° to 40°. The interstratifica- 
tion of a thin band of Skiddaw slate (No. 4), near the base, would 
indicate that these are some of the lowest beds of the whole 
volcanic series, and although at this particular spot the junction 
between the Skiddaw slate and the volcanic rocks is a faulted one, 
there is abundant evidence farther north (given in Survey Reports) 
of the gradual passage from the one series into the other, or, in 
other words, of the submarine character of the earlier volcanic 
deposits, though at a later period the volcanoes became wholly or 
almost wholly sub-aérial. Whether the entire thickness of more 
than 2500 feet, shown in the section, represents submarine volcanic 
deposits is doubtful; from analogy with other parts of the district 
this is probably noé the case. 
VOL. XVII. v 
