3GG 
THE GEOLOGIST. 
■vvings. In place of a vcin-st onc, however, there are certain accom- 
paniments of a pecuhar condition in the rock which are considered 
by the miner as bearing unfailing testimony of the proximity of ore ; 
these guides are called the " wcigh-beds" {e e' e" e'" in diagram), and 
are composed of soft decomposed limestone much resembling (although 
possessing an entirely different chemical composition) the clayey 
contents of the " slides," and often " cross-com-ses" associated Avith 
the lodes in Cornwall, and there teiTued " flookan." The position of 
these beds is immediately overlying the ore, both in the thick as well 
as the thin beds (see lignogTaph), but particularly the latter, where 
the "weigh" is said "to change into ore." The collective term in 
use for the various mineralized portions of the saddles is " bearing 
beds." Cutting across the saddles or bearing beds, as has already 
been mentioned, are the east and west fissures called " lums ;" their 
veins are usually of great magnitude, and are commonly entirely 
filled with mai'l and decomposed limestone, although in the imme- 
diate neighbourhood of the pipe-veins some ore proceeding from the 
saddles is mostly found attached to the cheeks of the vein. 
But if there is a great change in the structure of the vein, and the 
mode of deposition of the ore when the pipe-veins come to intersect 
the bearing beds, the change in respect of the nature of the minerals 
is greater still, the ore in the pipe and rake-veins being lead, while 
that in the saddles and limestone is almost always copper ; some lead as 
u.sually foiind at first in the saddles, but as the beds near the limestone 
the proportion of copper ore invariably increases, until the whole 
deposit consists of this mineral. The distance to wliich the ore is 
deposited in the bearing beds laterally divergent from the point of 
intersection of the pipes, amounts seldom to more than two or three 
saddles' breadth on either side, although there is no rule in the case ; 
the transverse deposits, i. e., those which are parallel with the saddle- 
joints, either on the wings or in the troughs entered often as much 
as eighty fathoms in one direction from the point of intersection 
with the pipe and limestone, and inasmuch as the limestone as stated 
above usually contains some ore at such points of junction, the saddles 
are in such cases said " to cany away the ore." 
The description of the mode of occurrence of the ore in the bear- 
ing beds as well as in the pipe- and rake-veins, in the jireccding 
paragi'aphs is a fail* resume, I believe, of the aggregate of the obsei-va- 
tions of the most experienced miners in the districts lying north, 
west, and south of Alstonfield, both in Staffordshire and the neigh- 
bouring county. 
From the consideration of appearances we naturally turn to the 
causes which have produced them ; and although it forms no part of 
my intention to give more in this article than something like a con- 
nected account of the phenomena obsei'vcd in these metalliferous 
saddles, as entered among my notes, there are yet some questions 
respectiug ilie histonj of the facts which need a brief recognition in 
this place. It has ah-eady been assumed that the plication of the 
beds has arisen from pressure laterally applied, and the origin of the 
