6 



KNOWLEDGE 



[Nov. 1, 1885. 



been named tbe " carboniferous " epocli or group. In 

 like manner we have designated the particular deposits 

 of that great period in which the coal chiefly abounds as 

 " the coal measures." Such names occurring in geolo- 

 gical books and on geological charts, and common!}' 

 quoted therefrom, naturally suggest the conclusion that 

 these are the only coal-bearing strata. Another soui'ce 

 of this popular inference has doubtless been supplied by 

 tbe speculations of some geologists concerning the state 

 of the world during the carboniferous epoch, speculations 

 involving the idea that once upon a time the whole 

 atmosphere of the earth was abnormally charged with 

 carbonic acid and aqueous vapour ; that vegetation just 

 then was exaggerated in its luxuriance ; that this period 

 followed a volcanic era which supplied the excess of 

 carbonic acid by eruptions of that gas from its craters, 

 the formation of the gas being due to the roasting of 

 limestone rocks and the combination of the lime with the 

 silicic acid of fused siliceous rocks. 



Going back to the article on Coal in the third edition 

 of the " Enoyclopiedia Britannica," for instance, I find 

 the following : — "The amazing irregularities, gaps, and 

 breaks (says Mr. Magellan) of the strata of coals, and of 

 other fossil substances, evince that this globe bas under- 

 gone the most violent convulsions, by which its parts 

 have been broken, detached, and overturned in various 

 ways, burying large tracts of their upper surfaces, with 

 all the animal and vegetable productions there existing 

 at the time of those horrible catastrophes, wbose epoch 

 far precedes all human records." 



This passage is curious and instructive ; it expresses in 

 a few words the prevailing geology of the period when 

 Sir Charles Lyell received his first geological teaching, 

 and which he devoted the greater part of his life's work 

 to correcting. He and his successors have shown us that 

 the facts revealed by careful examination of the earth's 

 structure may be explained consistently without the 

 invention of any "horrible catastrophes," or periods of 

 extravagantly violent volcanic convulsions, or deluges, or 

 periods of atmospheric floods of carbonic acid, or any 

 other sensational proceedings of nature far exceeding in 

 volume those now in progress. Allowing a sufficient time 

 for theii' operation, the forces that are now modifying the 

 crust and surface of the earth are capable of doing all 

 that has been done during the formation of the earth's 

 crust, with no greater or more frequent outbreaks of 

 exceptional violence than those which occasionally 

 disturb the 2_)resent epoch. 



In the eighth edition of the above-quoted national work 

 (that immediately preceding the new edition now in 

 progress), the following geological information is given. 

 " Coal is found in those strata designated the secondary 

 formation, or coal measures, and in seams varjnug from 

 an inch to forty feet." No mention is made, or indication 

 given, of the existence of coal in any other geological 

 region, thus justifying the commonly-accepted notion that 

 coal is an exceptional deposit, formed during an era when 

 all the world was undergoing an exceptional spasm of 

 exuberant vegetation. 



We now know that deposits of some kind of coal exist 

 in every great group of rocks that contain any vestiges of 

 life, and that coal is in course of deposition at the 

 present moment. 



The earliest deposit takes the form of graphite, 

 or "black-lead,'' which contains no lead at all, and is not 

 a " carburet of iron," as stated in many books, but is 

 nearly pure carbon. 



This, the softest of solids (I am not speaking of pulpy 

 softness due to semi-lluidity) — so soft that it can scratch 



no other solid and is scratcbable by nearly all, and is filed 

 away by the asperities of the smoothest writing-paper — 

 has the same composition as the hardest of all solids, 

 that which scratches every other solid and is scratchable 

 by none — the diamond. Graphite is found even in the 

 hypozoic rocks, or those lower down or more ancient 

 than any that bear the remains of organic beings. Much 

 has been written concerning the origin of graphite — 

 upon the question whether it is primary and purely 

 mineral carbon, or whether it is an altered vegetable 

 product. I must not be tempted to discuss this at any 

 length, but will simply quote the conclusions of a high 

 authority. 



Bischof (" Elements of Chemical and Physical Geo- 

 logy ") says, " The geologists who ascribe to the earth an 

 igneous origin, can adopt no other view tban tbat all 

 the carbon upon and in the earth is of secondary 

 origin, and therefore was not present at tbe jDeriod of 

 creation ; for the reducing agent of the iron ores would 

 not have remained in contact with ]5eroxide of iron and 

 other oxides in the state of igneous fusit)n without being 

 converted into carbonic acid and carbonic oxide gases, 

 thus causing the reduction of the oxides. Since the 

 entire group of unstratified crystalline rocks, which, 

 according to the plutonists, have been ejected from be- 

 neath, contain in their masses no carbon, this fact must 

 lead them to the conviction that this substance cannot be 

 an original formation." 



Bischof is by no means alone in concluding that all 

 isolated carbon found in the earth can " only be regarded 

 as a product of decomposition of carbonic acid, and it is 

 the vegetable kingdom which yielded and still yields this 

 product." The fact that we find such carbon lower 

 down or earlier than any remains of animal life does not 

 distui'b this conclusion. Vegetable matter being the 

 primarj' food of animals, they must have been jjreceded 

 by vegetables, and probably by immeasurable ages of 

 vegetable evolution, or of zoophyte (animal- plant) evolu- 

 tion, and these lower rocks which entombed the remains 

 of the links of life connecting plant with animal, having 

 been subjected to the metamorphic agencies of crushing 

 pressure and tbe high temperature that still exists at 

 great depths, could not preserve the forms, though they 

 may have retained the one non-volatile solid element of 

 these primordial living things. Graphite corresponds to 

 this. 



Anthracite, as Bischof says, " occupies an intermediate 

 position between coal and graphite," and is undoubtedly 

 of vegetable origin. It is both geologically and chemi- 

 cally intermediate, being frequently found in more 

 ancient rocks than tbose which beai' bituminous coal. 

 This, however, is not universally the case ; anthracite 

 also occurs in the same formations as bituminous coal, 

 and is even continuous with it, as will be exjilained 

 hereafter. 



Our richest seams of coal occur in the upper part of 

 the carboniferous group in the "coal measures" above- 

 named. The ai^pended table, copied from Mr. Morris's 

 chart, indicates their position. 



The table includes only the Paleozoic rocks where the 

 most ancient or primary traces of life are found. Below 

 them are Hypozoic or Metamorphic rocks, in which are 

 found no other traces of life than the ambiguous grajihite, 

 and below these the granite ; above them, a vast world 

 of later growth. 



So completely does the coal disappear from the majority 

 of our coi'.l-fields when we go below the upper scrius of 

 the carboniferous rocks, tbat the millstone grit has 

 received the name of the " Farewell Rock," experience 



