ON MINERAL VEINS IN CARBONIFEROUS LIMESTONE. 367 



sence of which were accounted for by their being transported thither during 

 submarine earthquakes. 



An examination of the veins in the former case might indicate the presence 

 of many other shells, and probably show the age of the veins of that district 

 to be Liassic or Oolitic. In the latter case, also, other remains might be found, 

 and yield additional confirmation of the views I have propounded. 



One reason for the non-discovery of organic remains has arisen from their 

 being generally of small size, and that the vein-stuff in which they have to 

 be sought for is often of a very intractable character, resisting the action of 

 the water by which it has to be dissolved before they can be washed out of 

 it, after which the residuum requires almost microscopic examination for 

 their separation. In the process of washing away the "dowks," it is inter- 

 esting to notice the very varied tints with which they colour the water, 

 according to the mineralogical character of the material to be operated upon, 

 which differs in separate districts, and on different levels or horizons in the 

 same mine. 



The organic remains thus obtained are occasionally even more varied, as 

 regards geaera and species, than if they had been derived from a given 

 horizon of stratified deposits, arising perhaps from the length of time within 

 which the fissure might have been open, and the necessarily mixed condition 

 consequent upon the fiUing up of the vein. Some from the Carboniferous 

 Limestone itself are associated with those which are foreign or derived. 

 In the case of the Charterhouse Mine on the Mendips, those which are of 

 Liassic age, and consequently derived, are in the proportion of about 90 to 

 30 from the older rocks within the walls of which they are found. In the 

 Carboniferous-limestone districts of Holwell and Frome, Rhaetic and Liassic 

 organisms are also in large proportion ; and the same may generally be said 

 throughout the Mendip range and South Wales. In North Wales and the 

 north of England, on the contrary, Carboniferous- limestone remains are the 

 most frequent ; those of later age are the exceptions, some of these being 

 Entomostraca of Permian species, which may be common to the two series, 

 and Foraminifera, which have a long range upwards. The precise later age 

 of the vein-infillings is therefore, in their cases, not so clearly defined as in 

 the south-west of England. In the Fallowfield Mine and the Silver Band 

 Mines, Flemincfites gracilis, a seed of the coal-period, occurs, whilst at Gras- 

 sington and Mold small particles of coal are occasionally present in the 

 " dowks," which at Fallowfield and in the Swaledale district are so like 

 material from the coal-shales that it is reasonable to infer that the veins are 

 contemporary with, or subsequent to, the coal-period. 



Nothing can weU be more remarkable than the Mendip veins with their 

 infillings of secondary age, high up on the Carboniferous-Umestone table- 

 land, and with no stratified deposits of lias within several miles. In the 

 case of the Charterhouse Mine, from the variety in the contents of the 

 fissures, there is ample evidence that a considerable time must have elapsed 

 within which they remained more or less open, and during which various 

 oceanic influences were at work. At 270 feet, the lowest depth of the 

 shaft, there is found a deposit of blue or greenish clay, 10 feet in thickness, 

 which has yielded the Liassic fossils given below. This, on the same level, 

 occasionally changes from a homogeneous marl to patches of a more conglo- 

 meratic material with enclosed water-worn pebbles. Higher up the vein it 

 becomes a dense conglomerate. Above this, sandy-looking deposits occur, 

 which, when washed, are seen to be almost entirely composed of the de- 

 tached stems of encrinites very much abraded, with small washed pebbles of 



