216 



♦ KNOWLEDGE • 



[Sept. 12, 1884. 



parts a grim and stern character to what is certainly 

 remarkable scenery. 



But to return. One of the great attractions of Peel is, 

 of course, its terrible castle, once the frequent residence 

 and long the formidable fortress of those Lords of Man, 

 the Earls of Derby. The prison vaults under the castle still 

 exist, fearful mementos of what feudal imprisonment meant ; 

 and here Elinor Cobham, Duchess of Gloucester, was im- 

 prisoned for life. This place is also connected with the old 

 Manx legend of a spectre dog, which it was a very serious 

 matter indeed for any one to encounter. The fine ruins 

 of the Cathedral of St. Germains, built 1245 A.D., should 

 be examined, and the insulated rock on which these re- 

 main — Sodor — possesses permanent interest, being, like the 

 historic lona, the place whence the original savages of the 

 islands first derived some of the lights — very broken they 

 were, in truth — of mediteval knowledge. Sodor, as every- 

 body knows, has puzzled etymologists considerably ; some 

 authorities declaring that it is simply derived from 

 Sudureys, which would mean merely the Southern Hebrides, 

 with which the Isle of Man was once associated. 



Very great improvements have been efiected of late years 

 at the principal ports of the island, and particularly is this 

 the case at Douglas. 



I obtained recently some special information on this 

 head from Sir Henry B. Loch, whose beneficent rule will 

 long be remembered by the Manxmen, and who is now the 

 Governor of Victoria, Australia. Sir Henry did much to 

 advance the material progress of the island, and in im- 

 proving the social and moral state of the people he was 

 ably seconded by Lady Loch. In the space of five years 

 only the tonnage entering Douglas was raised from a value 

 of £100,000 to £500,000, and the splendid sea defence 

 and docks constructed in the harbour are reckoned as 

 among the largest examples of solid concrete at the greatest 

 depth of water in the United Kingdom. 



(To be continued.) 



NOTES ON COAL. 



By Richard A. Proctok. 



IT has become a question of serious import whether we 

 may indeed look confidently for abundant supplies of 

 coal during many future years, or whether those have been 

 in the right who have told us that before the close of the 

 present century this country must feel the effects of the 

 over-rapid working of our chief coal-fields. 



I propose briefly to sketch what is known about the 

 origin of coal, and then to touch on the subject of the 

 supply of this mineral, with special reference to the 

 requirements of our own country. 



A mistaken impression is somewhat widely prevalent 

 that, in the coal-fields, we have the remains of ancient 

 forests ; in other words, it is supposed that, wherever there 

 was a forest in primeval times, there now exists a coal-field 

 of greater or less extent. In connection with this view, 

 also, the opinion is entertained that the forests now in 

 existence will, in process of time, and after due geological 

 changes, become the coal-beds of future ages. 



But although, as we shall presently see, the coal-fields 

 are undoubtedly due to the vegetation of former eras, it is 

 far from being the case that the primieval forests became 

 converted in a general way into coal. Conditions of a pecu- 

 liar, and to some extent exceptional, character were requi- 

 site for the formation of coal-fields. If we consider the 

 evidence given by the coal-fields themselves, we shall see 

 ■what these conditions wera 



The beds or seams of coal form but a small portion of 

 the thickness of the great geological group of strata to 

 which they for the most part appertain. This group is 

 called the carboniferous, and not uncommonly " The 

 Coal " ; but even where coal is most abundant, it forms 

 only a minute part of the whole mass. Thus it has been 

 estimated. Sir Charles Ljell tells us, that in South Wales 

 the thickness of the carboniferous strata amounts in all to 

 between 11,000 and 12,000 feet (or more than two miles);* 

 " but the various coal-seams do not," according to Professor 

 Phillips, " exceed in the aggregate 120 feet," or little more 

 than one-hundreth part of the whole. In North Lanca- 

 shire the carboniferous strata occupy a depth of more than 

 three and a half miles, with the same relative disproportion 

 between the thickness of the coal-seams and that of the 

 complete series of strata. Again, in 'Nova Scotia the coal- 

 bearing strata attain a thickness of more than three 

 miles, t Here no fewer than eighty seams of coal have 

 been counted (seventy-one having been exposed by the 

 action of the sea) ; but these seams are nowhere more than 

 five feet in thickness, and many are but a few inches thick. 

 Thus it is evident that the formation of coal can have been 

 in progress but for a short portion of the time during which 

 the great carboniferous series of strata was in process of 

 deposition. Throughout by far the greater portion of that 

 time other minerals were being deposited. 



It is next to be noticed that under each coal-seam a 

 stratum of older soil exists, in which there ai-e commonly 

 found the roots of ancient trees ; while above the coal there 

 is commonly a layer of shale or sandstone, in which not 

 unfrequently the trunks of those trees are found either 

 fallen or still in their original position, and only partly 

 converted into coal. The bark remains, but is transmuted 

 into coal ; the hollow of the trunk, decaying long before 

 the trunk gave way, is represented by a cast in sandstone. 

 Thus, if we try to picture to ourselves the state of things 

 which existed when such a seam of coal first began to 

 be covered up by the next higher deposit, we see that 

 there must have been trees standing erect above a layer 

 of vegetable matter, the roots of the trees being imbedded 

 in the soil which forms the deposit next below the coal. 

 The vegetable layers may probably have been two or three 

 times as thick as the resulting coal-seam, and were reduced 

 by pressure to their present thickness ; but such layers 

 cannot at any time have reached to the branches of the 

 forest-trees. Then the process of deposition began. This 

 can only have happened when some subsidence of the soil 

 had caused it to be submerged to a greater or less depth. 

 We can infer from the depth of the strata overlying the 

 coal-seams that this state of submergence continued in 

 many cases for a long period of time ; £md it is equally 

 clear that the formation of the vegetable layers themselves 

 must have been a process occupying a considerable time, 

 since tall trees grew before the next submergence took place. 

 So soon as submergence was complete, the tall trees 

 perished and began to decay. The stout trunks above the 

 vegetable layer were broken off and swept away by the 



* It is, perhaps, hardly necessary to remark that this depth has 

 not been measnred anywhere in a vertical direction. The thick- 

 ness of the several layers can be measured where they either crop 

 out, or show at the surface, or else come within the range of mining 

 operations ; and thus the total depth of the series can be estimated. 



t The way in which this has been made known is worthy of 

 notice. In the Bay of Fundy the tides run to an enormous height. 

 The tidal wave can be seen when it is stUl thirty mUes away, 

 advancing with a prodigious uproar, and rising sometimes to the 

 height of more than a hundred feet. These tremendous waves have 

 not only produced a continuous section ten miles long, through the 

 inclined strata, but by their action they sweep away continually the 

 whole face of the cliffs, and bring into view fresh sections year after 

 year. 



