208 



KNOVSTLEDGE 



[May 1, 1886. 



ficently displayed from the railway between Ti-ondlijem 

 and Storen, where the line crosses many of these valleys 

 with the step terraces extending up them and visible for 

 miles. They show that all these valleys within a geo- 

 logically recent period have beea nnder water, were arms of 

 fjords 600 feet deep at their present mouths, and there are 

 evidences to show that several alternations of rising and 

 fallin'T either of the land or the sea level have occnrred. 



We have only to suppose that similar conditions existed in 

 the carboniferous period to account for the covering up of 

 the lowest of the coal seams and the redepusiting and 

 recovering of other seams in successive altei-nations of the 

 level of such fjords or long, steep estuaries — always 

 remembering that the climate of the carboniferous period 

 (proved by its vegetation) was vastly more favourable to 

 luxuriant vegetation than that of arctic and sub-arctic 

 Norway. 



There is no difficult^' in accounting for the isolated trees, 

 reeds, etc., found in the coal-measures — some lying down, 

 some upright, and others inclining at all angles. The silt- 

 ing would take place at the upper end of the lake or fjord 

 simultaneously with the occasional downfall of vegetable 

 avalanches, and thus the trees and all other vegetation of 

 the denuded slopes would be bedded in the mineral matter 

 as we fiud them ; the probabilities of upstanding position 

 being largely increased by the fixing of the lower portion of 

 those trees that had sunk in such position in con.sec.uence 

 of the stony matter adhei'ing to their roots. A curious 

 result would be likely to follow in such cases. The tree 

 thus standing upright, or moderately inclined, would be 

 slowly surrounded by the mineral deposit, and at the same 

 time be slowly decomposing. If this decomposition of the 

 vegetable matter were completed before the tree became 

 wholly buried its place would be occupied by a tube, and 

 the nnburied upper portion would break oft', leaving the 

 tube open at the top. Into this open tube mineral matter 

 would of course descend, forming a coi'e or column occupying 

 the space formerly filled by the tree. Are such cores or 

 columns ever found in the coal measures 1 



The following shows that they are : — " In a colliery near 

 to Newcastle, say the authors of the ' Fossil Flora,' a great 

 numVier o{ Sigillaria; were placed in the rock as if they had re- 

 tained the position in which they grew. Not less than thirty, 

 some of them 4 or 5 feet in diameter, were visible within 

 an area of .50 yards square, the interior being sandstone, and 

 the bark having been converted into coal. The roots of one 

 individual were found imbedded in the shale, and the 

 trunk, after maintaining .a perpendicular cour.se and circular 

 form for the height of about 10 feet, was then bent over so 

 as to become horizontal. Here it was distended laterally, 

 and flattened so as to be only 1 inch thick, the flutings 

 being comparatively distinct. Such vertical stems are 

 familiar to our miners, nnder the name of coal pipes. . . . 

 These coal pipes are much di'eaded liy our miners, for almost 

 every year in the Bristol, Newcastle, and other coal-fields, 

 they are the cause of fatal accidents. Each cylindrical cast 

 of a tree formed of solid sandstone, and increasing gradually 

 in size towards the base, and being without branches, has 

 its whole weight thrown downwards, and receives no sup- 

 port from the coating of friable coal, which hsis replaced the 

 bark. As soon, therefore, as the cohesion of this external 

 layer is overcome, the heavy column falls suddenly in a 

 perpendicular or oblique direction, from the roof of the 

 gallery whence the coal has been extracted, wounding or 

 killing the workman who stands below." — Lyell's " Elements 

 of Geology," pp. 478-79 of fifth edition. 



Such a tube penetrating the bottom deposit and suddenly 

 opened when the upper part of the partially decomposed or 

 rotted tree fell down would naturally fill up to a given depth 



in a shorter time than would be necessary for the formation 

 of the same depth of deposit all around it, as the river 

 stream bearing the solid matter drifted over it. If there 

 were variations of material in the strata (as are found to 

 occur), these would net be rejJresented inside the tulie ; all 

 its materials would belong to the period succeeding the 

 exposure of its mouth. This is confirmed by the iisual 

 structure of these coal pipes. Sir Charles Lyell describes, 

 in the work aVjove (juoted, the interior stratification of several 

 of such trees which differ from the strata around them. In 

 one example "the layers of matter in the inside of the 

 tree are more numerous than those without ; but it is more 

 common in the coal measures of all countries to find a 

 cylinder of pure sandstone — the cast of the interior of a 

 tree — intersecting a great many alternate beds of shale and 

 sandstone, which originally enveloped the tree as it stood 

 erect in the water." 



Many of the trees found in the coal measures have the tubes 

 of a species of sprrorhis or serpida (marine worms that cover 

 themselves with an envelope or shell of limestone, and live 

 within it), showing long immersion in salt or brack'sh 

 water. 



As regards the composition of the strata immediately 

 covering the coal seams, Lyell says : " The more closely the 

 strata productive of coal have been studied, the greater has 

 become the force of the evidence in favour of their having 

 originated in the manner of modern deltas. They display 

 a vast thickness of stratified mud and fine sand without 

 pebbles, and in them are seen countless stems, leaves, and 

 roots cf terrestrial plants, free, for the most part, from all 

 admixture of marine remains — circumstances which imply 

 the persistency in the same region of a vast body of fresh 

 water." 



We must remember that the thickness of these deposits 

 above the coal seams is ver}' great, from 600 to 1:2,000 feet 

 in the Biitish Isles. The theory favoured by Lyell, that 

 the coal is formed by rafts of vegetable matter — like those 

 of the Mississippi — brought down to the open sea and there 

 deposited at, or a little above, surface level, demands enor- 

 mous subsidences and upheavals, which could scarcely have 

 occurred thus on the open sea-shore without completely 

 marine conditions prevailing during some parts of the time. 

 Besides this, a raft of pure vegetable matter as free from 

 mineral material adulteration as ordinary coal, and extend- 

 ing over some hundreds of square miles, demands a very big 

 river indeed. I read a paper on this subject at the Bir- 

 mingham meeting of the British Association in 186.5, and a 

 very lively discussion followed, in which Sir Roderick ISIur- 

 chison. Sir C'hailes Lyell, John Phillips (the President of the 

 year), and Principal Dawson took part. Lyell advocated 

 the raft theory, and some amusement followed when this 

 difficulty of finding a river big enough was raised, and was 

 connected with his own published accounts of the probable 

 insular conditions and climate of the period of the coal 

 measures. 



One of the most characteristic— I may say the specially 

 characteristic — mineral deposit of the coal measures is that 

 which the miners call the " linstey " or " iinsey " rock, from 

 its resemblance to the striped fabric, Iinsey, which is the 

 usual material of their wives' skirts. It is a sandstone 

 striped with dark, black lines due to fibres of carbonaceous 

 matter. Some of these stripes are very thin, I hope to have an 

 interesting illustration of this rock in my next paper. My 

 explanation of the formation of this rock is that during the 

 winter or other flood periods of its formation the white non- 

 carbonaceous streaks were deposited in the fjord or lake, 

 and that during other periods, when but little mineral silt 

 was deposited, the vegetable matter from the wooded hill- 

 sides, was deposited through the comparatively clear water 



