296 MINING 



granite quarry will exhibit very distinct lines, conforming, more or less, to the hori- 

 zontal known to the quarrymen as the bedway which would appear almost sufficient 

 to place those rocks for certain purposes amongst the stratified ones. 



It is commonly stated that the unstratifled rocks possess a nearly vertical position, 

 the stratified rocks assuming more nearly a horizontal one. There are numerous 

 examples adverse to this view ; indeed, it must be regarded as a hasty generalisation 

 the bedway of the granite approaching very nearly to the horizontal, while we 

 often find the truly stratified rocks in a vertical position. 



Where the older rocks graduate down into the plains, rocks of an intermediate 

 character appear, which, though possessing a nearly vertical position, like the unstra- 

 tified and non-fossiliferous rocks, contain a few vestiges of animal beings. These 

 were formerly called transition, to indicate their being the passing links between 

 the first and second systems of ancient deposits ; some of them are distinguished 

 by their fractured and cemented texture, for which reason they are sometimes called 

 conglomerate. These transition rocks form part of the Palaosoic series of modern 

 geologists. 



Between the older and the secondary rocks, another very valuable series is inter- 

 posed in certain districts of the globe ; namely, the coal-measures, the paramount 

 formation of Great Britain. The coal-strata are frequently disposed in a basin-form, 

 and alternate with parallel beds of sandstone, slate-clay, ironstone, and occasionally 

 of limestone. 



As a practical rule it may be here stated that, in every mineral formation, the 

 inclination and direction are to be noted ; the former .being the angle which it forms 

 with the horizon, the latter the point of the azimuth or horizon towards which it dips, 

 as west, north-east, south, &c. The direction of a bed is that of a horizontal lino 

 drawn in its plane ; and which is also denoted by the point of the compass. Since 

 the lines of direction and inclination are at right angles to each other, the first may 

 always be inferred from the second ; for when a stratum is said to dip to the east or 

 west, this implies that its direction is north and south. 



The following terms have been used to express dissimilar conditions in mineral 

 deposits, well known to the practical miner. 



Masses are mineral deposits, not extensively spread in parallel planes, but irregular 

 heaps, rounded, oval, or angular, enveloped in whole or in a great measure by rocks 

 of ;i different kind. Lenticular masses, being frequently placed between two hori- 

 zontal or inclined strata, have been sometimes supposed to be stratiform themselves, 

 ;md have been accordingly denominated by the Germans liegende Stocke, lying-heaps, 

 or blocks. 



The orbicular masses often occur in the interior of unstratified mountains, or in the 

 bosom of one bed. These frequently indicate pre-existing cavernous spaces, which have 

 been filled in with metalliferous or mineral matter. 



Nests, Concretions, or Nodules, are small masses found in the middle of strata ; the 

 first being commonly in a friable state ; the second often kidney-shaped, or tuberous ; 

 the third nearly round and encrusted, like the kernel of an almond. 



Lodes, or Veins, are flattened masses, with their opposite surfaces not always parallel. 

 These sometimes terminate like a wedge, at a greater or less distance, and do not run 

 parallel with the rocky strata in which they lie, but cross them in a direction not fur 

 from the perpendicular ; often traversing several different mineral planes. The lodes 

 are sometimes deranged in their course, so as to pursue for a little way the space 

 lietween two contiguous strata ; at other times they divide into several branches. 

 The matter which fills the lodes is for the most part entirely different from the rocks 

 they pass through, or at least it possesses peculiar features. 



This mode of occurrence suggests tlio idea of clefts or rents having been made in 

 the stratum posterior to its consolidation, and of the vacuities having been filled with 

 foreign matter, either immediately or after a certain interval. There can be no doubt 

 as to the justice of the first part of the proposition, for there may be observed round 

 many lodes undeniable proofs of the movement or dislocation of the rock ; for ex- 

 ample, upon each side of the rent, the same strata are no longer situated in the same 

 plane as before, but make greater or smaller angles with it ; or the stratum upon one 

 side of the lode is raised considerably above, or depressed considerably below, its 

 counterpart upon the other side. With regard to the manner in which the rent has 

 been filled, different opinions may be entertained. In the lodes which are widest near 

 the surface of the ground, and graduate into a thin wedge below, the foreign matter 

 would seem to have been introduced as into a funnel at the top, and to have carried 

 along with it portions of rounded gravel, and sometimes, though rarely, organic re- 

 mains. In other, but very exceptional, cases, lodes are largest at their under part, 

 and become progressively narrower as they approach tho surface. From this cir- 

 cumstance, it has been inferred that the rent has been caused by an expansive force 



