the Coal fields of the northern and central parts of England shall be exhausted.* Fig. 3. Section of inclined Carboniferous strata, overlaid unconformably by horizontal strata of New Red Sandstone, Lias, and Oolite, in Somersetshire. This Section illustrates the manner in which Carboniferous strata have been elevated at their extremities around the circumference of a basin, and depressed towards its centre, and also intersected by fractures or Faults. See V. 1. pp. 394, 405. In Section 1, 2, of this Plate, no notice is taken of the Faults which intersect the Coal basins. PLATE 66. V. I. p. 394, Note. Fig. 1. Section of the strata composing the Silurian System, and the lower part of the Carboniferous System, on the frontiers of England and Wales. (Murchison.) Fig. 2. Appearance of Faults intersecting the Coal formation near Newcastle-on-Tyne, copied from a portion of one of Mr. Buddle's important sections of the Newcastle Coal field, in the Transactions of the Nat. Hist. Society of Northumberland, V. I. Pt. 3, Pl. XXI. XXII. XXIII.+ The advantages *The lower and richest beds of this Coal district are not only raised to the surface, and rendered easily accessible around the external margin of the basin, but are also brought within reach in consequence of another important elevation, along an anticlinal line, running nearly E. and W. through a considerable portion of the interior of the basin, in the direction of its longer diameter. I feel it a public duty to make known an act of Mr. Buddle, which will entitle him to the gratitude of posterity, and has set an example, which, if generally followed in all extensive collieries, will save the lives of thousands of unfortunate miners, that must otherwise perish for want of information which can, at this time, be easily recorded for their preservation. This eminent Engineer and Coal resulting from these Interruptions of the continuity of the strata are pointed out in pp. 406, 407. A large portion of the surface of these strata near Newcastle is covered with a thick bed of diluvial Clay interspersed with Pebbles, in the manner represented at the top of this Section. The effect of this Clay must be to exclude much rain-water that would have percolated downwards into the Coal mines, had strata of porous Sandstone formed the actual surface. PLATE 67. V. I. p. 417. Fig 1. represents the case of a valley of Denudation in Viewer has presented to the Natural History Society of Newcastle, copies of his most important plans and sections, accompanied by written documents, of the under ground workings in the Collieries near that town, in which all those spaces are carefully noted, from whence the Coal has been extracted. Every practical Miner is too well acquainted with the danger of approaching ancient workings in consequence of the accumulation of water in those parts from which Coal has been removed. The sudden irruption of this water into a mine adjacent to such reservoirs is occasionally attended with most calamitous and fatal results. See History of Fossil Fuel, the Collieries and Coal Trade, 1835. P. 249 et seq. The distates of humanity which prompt us to aid in the preservation of human life, no less than the economical view of rendering available at a future time the residuary portions of our beds of Coal, which will not now repay the cost of extracting them, should induce all proprietors and other persons connected with Coal Mines, and especially Engineers and Coal Viewers, to leave to their successors a legacy, which will to them be precious, by preserving minute and exact records of the state of the coal in their respective districts. It can, however, scarcely be expected, that such measures will be generally and systematically adopted throughout the many Coal fields of this country, unless the subject be legislatively taken up by those official persons, whom it behoves, as guardians of the future welfare of the nation, to institute due measures, whilst the opportunities exist, for preventing that loss of life and property, which a little attention bestowed in season, will preserve to posterity. stratified rocks, terminated abruptly by a cliff on the sea-shore; this figure is intended to illustrate two causes of the production of Springs by descent, of water from porous strata at higher levels; the first, producing discharges in valleys of Denudation, along the line of junction of porous with impermeable strata; the other, by the interruption offered to descent of water by Faults that intersect the strata. The Hills A, C, are supposed to be formed of a permeable stratum a, a, a", resting on an impermeable bed of Clay b, b', b". Between these two Hills is a Valley of Denudation, B. Towards the head of this Valley the junction of the permeable stratum a, a', with the Clay bed b, b', produces a spring at the point S.; here the intersection of these strata by the denudation of the valley affords a perennial issue to the Rain water, which falls upon the adjacent upland plain, and percolating downwards to the bottom of the porous stratum a, a', accumulates therein until it is discharged by numerous springs, in positions similar to S, near the head and along the sides of the valleys which intersect the junction of the stratum a, a', with the stratum b, b'. See V. I. p. 417.* The Hill C, represents the case of a spring produced by a Fault, H. The Rain that falls upon this Hill between H, and D, descends through the porous stratum a", to the subjacent bed of Clay b". *The term Combe, so common in the names of upland Villages, is usually applied to that unwatered portion of a valley, which forms its continuation beyond, and above the most elevated spring that issues into it; at this point, or spring head, the valley ends, and the Combe begins. The conveniences of water and shelter which these springheads afford, have usually fixed the site of the highest villages that are planted around the margin of elevated plains. The inclination of this bed directs its course towards the Fault H, where its progress is intercepted by the dislocated edge of the Clay bed b', and a spring is formed at the point f. Springs originating in causes of this kind are of very frequent occurrence, and are easily recognised in cliffs upon the sea-shore.* In inland districts, the fractures which cause these springs are usually less apparent, and the issues of water often give to the Geologist notice of Faults, of which the form of the surface affords no visible indication. See V. I. p. 418, Note. Fig. 2. Section of the valley of Pyrmont in Westphalia. A cold chalybeate water rises in this valley at d, through broken fragments of New Red Sandstone, filling a fracture which forms the Axis of Elevation of the valley. The strata are elevated unequally on opposite sides of this fracture. See V. I. p. 419. (Hoffmann.) Explanation of Letters referred to in this Figure. a. Keuper. b. Muschelkalk or shelly Limestone. c. Variegated Sandstone. d. Cold chalybeate Springs rising through a fracture on the Axis of Elevation of the Valley. M. The Muhlberg, 1107 feet above the sea. Fig. 3. Section reduced from Thomas's survey of the mining district of Cornwall (1819;) it exhibits *Three such cases may be seen on the banks of the Severn near Bristol, in small faults that traverse the low cliff of Red Marl and Lias on the N. E. of the Aust Passage. See Geol. Trans. N. S. Vol. I. Pt. II. Pl. 37. the manner in which the Granite and Slate near Redruth are intersected by metalliferous Veins, terminated abruptly at the surface, and descending to an unknown depth; these Veins are usually most productive near the junction of the Granite with the Slate, and where one Vein intersects another. The mean direction of the greatest number of them is nearly from E. N. E. to W. S. W. They are intersected nearly at right angles by other and less numerous Veins called Cross Courses, the contents of which usually differ from those of the E. and W. veins, and are seldom metalliferous. The Granite and Killas and other rocks which intersect them, e. g. Dikes and intruded masses of more recent Granite, and of various kinds of porphyritic rocks called Elvans (see Pl. 1, a 9. b. c.) are considered to have occupied their present relative positions, before the origin of the fissures, which form the metalliferous Veins, that intersect them all. (See V. I. p. 411.*) * In Vol. I. P. 413, Note, a reference is made to some important observations by Mr. R. W. Fox on the Electro-magnetic actions which are now going on in the mines of Cornwall, as being likely to throw important light on the manner in which the ores have been introduced to metallic veins. The following observations by the same gentleman in a recent communication to the Geological Society of London, (April, 1836,) appear to contain the rudiments of a Theory, which, when maturely developed, promises to offer a solution of this difficult and complex Problem. If it be admitted that fissures may have been produced by changes in the temperature of the earth, there can be little difficulty in also admitting that electricity may have powerfully influenced the existing arrangement of the contents of mineral veins. How are we otherwise to account for the relative positions of veins of different kinds with respect to each other, and likewise of their contents in reference to the rocks which they traverse, and many other phenomena ob |