238 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[August, 



The coal is the most bituminous and the best adapted for economical pur- 

 poses of any yft known. 



The Lancashire coal field occupies a considerable area, and is connected 

 with that (pf Yciilisliire. It includes perhaps the most perfect series of the 

 rocks of the period anywhere existing, and consists as usual of sandy beds 

 and shales, alternating with a large number of coal seams, seventy-five of 

 which ("whose total thickness is 150 feet) are described. In its upper part 

 occurs a pale blue limestone of freshwater origin, vihich is again met with in 

 other coal fields nearly a hundred miles distant, and appears also at various 

 intermediate points. 



The South Staffordshire coal field is remarkable as the only representative 

 of the Carboniferous rocks in that part of England, the millstone grit and 

 Carboniferous limestone being both absent. It exhibits a great preponderance 

 of shale, and the number of its coal seams is only eleven, but the thickness 

 of one of these is unusually great, amounting to upwards of 30 feet in some 

 places. 



The South Welsh coal field contains about 95 feet of coal distributed in 

 about a hundred seams, the most powerful of which is about nine feet thick. 

 The associated shales and sandst<ines are of very unusup.l thickness, and they 

 contain besides coal an abundant supply of ironstone ore. A considerable 

 part of the coal in this district is non-hituminous, and distinguished by the 

 name of Anthracite. 



Besides these, there are numerous smaller deposits of coal in the Middle 

 and of West, and in Wales, all of which possess local importance, but which 

 we cannot now stop to describe. 



The basin of Clyde in Scotland, is no less interesting for its carboniferous 

 deposits than important from extent and value. In this district, the Old red 

 sandstone is thr general base of the coal strata, thick sandstones occasionally 

 containing coal, taking the place of the lower carboniferous limestone. Thin 

 beds of limestone then succeed, and on these rest the greet mass of the coal, 

 bearing strata, which greatly reseralde the similarly situated beds in England, 

 but which include seams of ironstone ore yet more valuable. There appears, 

 however, to be a freshwater limestone in this part of Scotland underlying the 

 coal measures, and possildy contemporaneous with a bituminous shale in the 

 North Stafl^ordsbire coal field. 



The coal seams in the Cl>de valley amount in number to eighty-four, hut 

 they are mostly thin ; the coal, however, is good. The total thickness of the 

 deposit is estimated at about 5,000 feet. 



The coal fields of Ireland are not unimportant, though they have hitherto 

 been little worked. The principle one worked is that of Leinster, and as 

 much as 20 or 30 feet of bituminous coal have be n found in another small 

 field near Tyrone. In Connaught there is also a supply of ironstone ore. 



France and Belgium both contain a considerable number of coal fields, but 

 they are njostly of small dimensions, and in the latter country are greatly 

 disturbed, inclining at a considerable angle to the horizon, and worked like 

 mineral veins. The French coal fields are all of very small size. 



Russia is not without an extensive series of strata of the date of the Car- 

 boniferous rocks ; and in the northern part of the empire there seems to be 

 a prospect of workable coal, the lowest beds of the system containing (as in 

 Yorkshire) a few seams of variable thickness, but of great value. In the 

 south of Russia, very good bituminous and anthracite coal is found in con- 

 siderable abundance, but the beds are much disturbed by faults. 



North America contains coal-bearint: strata of great value, and of enor- 

 mous extent, a gigantic coalfield existing in the Western Slates, and offering 

 every prospect of success in the working. The coal measures here, as in 

 Europe, form the uppermost part of the carboniferous series, and the numlier 

 of seams hitherto know is about ten, having an aggregate thickness of 50 

 feet. There is one bed of 30 feet, worked like a quarry from the surface. 



In Van Diemeir's Land, and probably in several parts of Asia, there are 

 strata of the Carboniferous period, greatly resembling those of our own 

 island, and consisting of limestones overlaid by coal-bearing strata. Much 

 yet remains to be done in making out satisfactorily the true position of these 

 strata with referenre to the well-known Carboniferous series of Europe. 



Wp could make manv oilier interesting extracts, hut as the book is 

 n small one ue do not like to borrow miicli from its pages. We will, 

 however, conclude with another extract taken from the second part, 

 Practical Geology. 



Vimrul Veins, and the extraction of Metallic Ores from them. 



Mineral veins are repositories in rocks of a flat or tabular shape, which 

 traverse strata without regard to their stratification, having the appearance 

 of rents formed in the rucks, and afterwards filled up by mineral matter, 

 which differs, more or less, from that of the rocks themselves.* 



Both veins and dykes, however, are fissures filled with ndneral matter, and 

 they differ from one another rather in their contents than in the form and 

 nature of their bounding walls. The cracks are called veins when they con- 

 tain crystalline rrjirierals, usually associated with metalliferous ores; they 

 vary gnaily in bnnzorital extent, they pass, though not indifferently, through 

 all the roi ks met with in their downward progress, their breadth is infinitely 

 irregular, and their i-imtents are rarely of equal value fur any great distance, 

 but have becume richer or p inrer, according to the action of causes which at 

 present are very bit e un Ifrstnod. 



Veins usually occur in a position nearly vertical, but this is by no means 



1 given by Werner, and can hardly be improved or added to at 



always the case, although the amount of inclination to the horizon is seldom 

 less than 45°; they have, in most cases, a very regular direction, appearing 

 in sets parallel or else at right angles to one another. The veins profitable 

 for working, in England, usually run east and west, or nearly in that direc- 

 tion, and '.bey appear to have reference to the general structure of the 

 country. ...... 



The indications on the surface by which the existence of metalliferous 

 veins is made known to the miner, form an interesting subject of inquiry, im- 

 mediately connected with Geology ; but it is rarely the case that any very 

 direct application of science gives the first hint of the presence of subterra- 

 neous riches, because the surface has almost always been exposed to some 

 denuding action by which the out-crop of the vein has become distributed in 

 the form of gravel, while, on the other band, a similar action has covered the 

 original surface with the debris of other rocks, preventing the Geologist from 

 tracing the line of the vein, or determining its direction and other attendant 

 circumstances. Practically, almost all mining operations in a district are 

 preceded by the occasional discovery of metalliferous ores in gravel, and the 

 tracing this gravel to its source is usually a work in which no knowledge of 

 the subject or science ot mining is called into play. In many countries, es- 

 pecially in the rich gold districts of Russia, and even of America, and in the 

 tin mines of Banca, the method of washing river sands and gravels for the 

 sake of the heavier particles of ore which they contain, and which sink in 

 water more readily than the sand itself, forms not only an important but al- 

 most the only source of supply, and the actual veins have not been reached. 

 In our own country, the search after Stream tin, as the Cornish stanniferous 

 gravels are called, is still occasionally a profiiable employment, although the 

 source of supply is very soon discovered and the vein worked regularly and 

 systematically. 



The art of tracing stream ores to the vein, called in Cornwall shoading, is 

 generally followed by the sinking of shallow pits, by means of which there is 

 obtained a rough approximation to the direction and probable extent of the 

 vein. If it is founrl to be right-running, that is, to have the same general 

 direction as the valuable mines of the same mineral in the district, it is then 

 advisable to commence work regularly and systematically, by sinking a ver- 

 tical shaft at some distance from the vein, with the intention of coming upon 

 it at a certain depth. When the hang or dip of the vein is consideralile this 

 is however souiewhat hazardous ; anil in cases where it is very slight, it is 

 not unusual, in some districts, to sink upon the actual vein itself, although 

 this metlioil is hardly considered economical ruining, or advisable, if the vein 

 be likely to yield a good return. 



Connected with these first operations, and almost at the same time as the 

 commencement of the sinkings, it is generally necessary to drive what is called 

 an adit level, or, in other words, a nearly horizontal gallery at the lowest 

 convenient depth which will admit of the water of the mine running off and 

 escaping. If the vein be discovered near a hill side, the adit level is so driven 

 as to drain the mine at the lowest point of the hill into the nearest stream 

 in the valley. Drainage is one of the very first things to be considered in 

 mining, since, without a convenient system adopted to get rid of superfluous 

 water, the operations must soon be stopped, either by water running in from 

 the neighbouring strata, or the accumulation of surface water and rain enter- 

 ing by the shaft. 



Although the method of discovering the existence of mineral veins by 

 tracing metalliferous gravel to its source is often applicable, it is by no means 

 always so ; and, in a district known, either in this or other ways, to contain 

 numerous veins, it is often worth while to speculate even where there are no 

 surface indications whatever. A method is adopted in Cornwall, called 

 costeaning, in cases of this kind. It is derived from the knowledge of the 

 law of the distribution of mineral veins in the district, and is more or less 

 likely to succeed, according as the knowledge of the experimenters is more 

 or less accurate In this case a spot is selected by an experienced person, as 

 the most likely to be near the outcrop of a good vein. On this spot a pit is 

 sunk to a small depth, and there is, of course, a chanceof success in this first 

 operation. Sliouhl it, however, fail, the next step is to drive a gallery from 

 the pit a short distance in opposite directions, at right angles to the general 

 direction of the lodes in the neighbourhood. If, in this way, they do not 

 "cut the lode," they next remove a few fathoms in the direction of the gal- 

 leries, and repeat the same process, and this they do till they either find the 

 vein or give up the speculation in despair. It is not easy to imagine a method 

 simpler or more certain than this, and it is peculiarly interesting as being 

 founded on correct Geological and mining principles. 



The underground-work of a mine, when the vein has been discovered and 

 its extent and probable value are ascertained, is a part of the subject on 

 which I shall not here dwell. Systems of galleries are usually driven at 

 depths about ten fathoms asunder and the ore is taken away between each 

 of these in succession, the roof of the mine being kept from falling in, partly 

 by timber props and paitly by rulibisb left to support it. The ore is sepa- 

 rated from the rock almost always by blasting, and is generally lifted by 

 machinery from the bottom of the shaft to the surface. 



The Gauge Qnctilion. Erils of a diversity of Gauge and a Remedy. 

 By Wyndiiam ii.\RDi.NG. With a Map. We.ile : 8vo., pp. 62. 



Though it be neither a short nor easy task to turn public attention 

 in Engl. aid to a new subject, it cannot bo denied that the general feel- 

 ing v\lieii it haa acquired a new direction is exhibited with ample 

 Warmth and energy. "The Gauge Question," is a case in point. 



