84 REPORT—1858. 
as cleat, and which has often been regarded as a sort of crystallization; the author, 
however, from various facts and reasonings, is decidedly of opinion that it is nothing 
but jointing in a state of extreme development. Notwithstanding cleat being some- 
times, as in pure coal, apparently as illimitable as mineral cleavage is in calcite or 
fluor-spar, the author contends, that in ordinary coal it is undistinguishable from 
the approximate jointing of many ancient argillaceous deposits. The paper con- 
cluded by some observations on the so-called slaty cleavage in the brown and purple 
shales of Cork: Professor King considers it as highly developed or cleat-like joint- 
ing, belonging to one of the equatorial sets, and having had its planes forced into a 
nearly vertical position by pressure exerted in a particular direction when the beds 
were thrown into their present anticlinal and synclinal rolls: he considers that the 
pressure was not sufficient to produce any other structural modification, or in other 
words, that it was insufficient to bring the divisional planes in immediate contact, as 
in true slate rocks; hence the Cork shales generally are not illimitably cleavable, as 
is the case with the former. 
On the Geology of the Lake District, in reference especially to the Meta- 
morphic and Igneous Rocks. By J. G. Marsnatt, F.G.S. 
I propose in the present paper to confine my observations to the Cambrian and 
older Silurian rocks of the Lake District, below the Coniston limestone ; consisting 
of an alternating series of igneous and sedimentary strata, all of which have been 
more or less acted upon by central heat. 
I shall endeavour to show that the phenomena observed may be best explained 
by the supposition, that the whole series of rocks, granites included, are metamor- 
phic sedimentary strata, iv situ, or in their natural order of position ; and that the 
slaty rocks alternating with the porphyries are to be accounted for on the supposition 
that they are by chemical composition less fusible, less easily acted upon by heat, 
than the porphyritic beds, and have therefore been only hardened, retaining their 
cleavage and stratified structure, whilst the more fusible rocks have been changed 
into porphyries. 
The two oldest rock formations of the Lake District, the clay-slate of Skiddaw and 
Saddleback, and the greenstone slate of Helvellyn and Scaw Fell, have, as is well 
known, the usual north-east and south-west strike and south-east dip of the rocks of 
the same age in Wales and Scotland. It is evident also that the district occupied by 
them includes an anticlinal axis, for we find the greenstone slate on the northern 
and north-west border of the clay-slate, as at Binsey, at the foot of Bassenthwaite, 
dipping north or north-west, The first step in describing the physical structure of 
the district will therefore be to ascertain the position of this anticlinal axis. I believe 
that this point has not yet been completely or satisfactorily made out, and it was the 
first object of my recent walks over this country to gain some fresh light on the sub- 
ject. There is perhaps no great geological interest attached to the ascertainment of 
this point, considered as an isolated fact ; but considered in reference to the inquiry 
into the relation of the granites of this district to the sedimentary rocks, it is of 
some importance. 
This inquiry into the correlation of granite and its accompanying metamorphic 
rocks with the sedimentary strata, whose age is known by their organic remains, has 
only lately attracted much notice from geologists. The vast labour of ascertaining the 
true age and order of superposition of the whole range of sedimentary rocks chiefly by 
their organic remains, had to be first accomplished. Accordingly we find that Sedg- 
wick, in his description of this district, has not entered into the question at length 
or indetail. Inhis letters to Mr. Wordsworth, he gives a section, which he is careful, 
however, to tell us is only an ideal or explanatory, not an actual section of the rocks 
of the district, showing their order of superposition. Here the Skiddaw granite is 
placed at the base of the series of rocks, and in the anticlinal axis of the district. 
This, though professedly only a provisional section, is one remarkable instance, 
with innumerable others, of the very general disposition amongst geologists, to 
assume tacitly that the origin and position of granite in the order of superposition 
of rocks is peculiar,—quite distinct from that of all sedimentary strata. Accordingly 
the granite apparently at the base of the clay-slate would be assumed to be in its 
