WATSON — XOTKS ON METALLIFliKOU.S SADDMIS. 
309 
the naliiro of their ore contents, and, parlly on tliis account, it has 
been remarked at the commencement of this notice that the saddles 
must not be chT,ssed indiscriminately with, but rather must be consi- 
dered apart from, the general vein-system of the districts in which 
they occur. Of course the separation cannot rest alone on the ground 
of a change in the description of the ore, since many such changes, 
and often from lead to copper, frequently occur in depth in true veins. 
The real distinction lies in the mechanical position of the ore, which, 
it would seem, gives a classification for the saddles between veins and 
bedded deposits ; and this arrangement will be further confirmed if, 
considering that the latter mostly comprehend mineral accumulations 
introduced from above, and the former those injected from below, the 
agency of the lums be rega^'ded in a two-fold light— first, as 
originally giving passage to copper-bearing solutions, with which 
their other mineral contents were at one time largely impregnated ; 
and, secondly, by afterwards permitting a free electrolysis of the 
salts by which the copper was determined to the fissures in the 
saddles, and by then, or after, acting chemical changes resolved into 
sulphurets (copper pyrites) as now found.* Thus conceived, the 
segregation of the ore in the saddles is a special phenomenon, and 
deserves, as I hope I may have succeeded in some measure, at least, 
to show, a separate and attentive consideration at the hands of phy- 
sical geologists. It is not to be confounded with what inr Flintshire 
and elsewhere in the mountain-limestone mining-districts are termed 
"flats," or "flat veins," notwithstanding that it more nearly resembles 
those descriptions of deposits than any others. Still it is widely 
diSerent, since as on one hand flat veins, as their name implies, are, 
comparatively speaking, horizontal veins, and often occupy a plain 
corresponding irregularly with the stratifications, so, on the other 
hand, the constant position of the ore in certain beds, as well as cer- 
tain parts of those beds, is, beyond all doTibt, the distinguishing 
peculiarity of the general phenomena of the saddles. 
In the foregoino- observations I have endeavoured to describe as 
neai'ly as possible the average of the appearances presented by the 
bearing beds of the Ecton district in the limestone ; but, as before 
mentioned, the same phenomena are observable in the Upper Lime- 
stone shales. They do not, however, merit any separate description 
beyond the statement that they are similarly mineralized, are equally 
traversed by lums, and have the same mechanical relations with the 
neighbouring veins and with the associated strata. 
* Where galena is the associated ore, copper seldom occurs in any other form 
than as copper pyrites, a fact worthy of remark in connection with the para- 
gonesis of metallic minerals. 
VOL. III. 
