302 
THE GEOLOGIST. 
tliroiig'li tlicm. These veins arc seldom higlily inclined as regards 
the relationsliip of their plane to the vertical plane of the rocks ; and 
considered with regard to their contents, only become productive in 
the immediate vicinity of, or at their conjuncture with, the pipe 
veins. It is, indeed, questionable whether they may exist even as 
fissures at any very great distance from the pipes ; at any rate, their 
origin may be safely assumed as contemporaneous. They are not 
often twitched, or, in other words, the spaces between the walls 
seldom present any great irregularities of size, such as commonly 
arise where the edges of the strata, originally opposite, by the nature 
of the fault are brought to diiferent levels. The direction of the 
rake veins varies, but a great number have been observed to run 
north-north-west to north-west. Crossing them, usually at nearly 
right angles, are other similar veins, which however must not be 
confounded with another set of great fractures which extend east and 
west, or nearly so, through a considerable extent of the country, and 
frequently intersect the saddle-beds in the direction of their strike. 
These fissures are locally known as " lums," this name having an analo- 
gous signification in mining language with what are elsewhere called 
cross-courses, although they differ essentially from these both in 
their mineral contents as well as in their effects on the veins with 
which they are associated and cut across. 
The lignograph, fig. 3, represents an ideal block, or parallelepiped, 
of the country in the neighbourhood of the Ecton and Dale mines 
without reference to the surface, and exhibits the strata, 1st, as they 
would be seen in vertical section on their line of strike ; and 2nd, as 
they would be seen in vertical section in the direction of their dip. 
The plane A B E F shows the contorted beds, or saddles, and those 
which are superincumbent but not contorted, h c d e: A B E F \s 
also the plane of the cross-course, called the lum, which consequently 
intersects the saddles vertically. The general features of the pipe- 
vein E E' in this diagram have been already explained, but E g, 
E g', E g" will show the connectionship of this vein and the rake- 
veins, as seen in plan ; the bearing of the rake-veins is north-east, 
south-west, and south-east. The gradual dying out of the con- 
tortions towards their crop at the surface, where they foiTu, as 
already stated, merely waved strata, a' a', explains itself by the 
dotted lines x y z. The dotted line o o' is supposed to proceed from 
saddle-beds much lower in the series (see also p. 365j, and which 
consequently ci'op out a great deal farther to the south. 
When considering the origin of metalliferous accumulations 
whether in igneous or stratified formations, any peculiarities in the 
composition of the rocks are as important to notice as are differences 
of stractui'e in the same I'ocks. It may be, therefore, here mentioned 
that many of the beds in the vicinity of the saddles, at Ecton and 
elsewhere, are highly charged with silica — either in a segTCgated 
form as pseudo-strata intercalated between the coursings of the 
stone, or by a species of pseudo-morphism : a bed of limestone, while 
retaining many of the marks of its sedimentary origin, is wholly, or 
