Dec. 1, 1885.] 



KNOWLEDGE 



41 



bituminous matter, leaving these vacancies. It burns as 

 coke burns, allowing for the difference of physical struc- 

 ture ; a little tlame is given off, but this flame is (in 

 perfect anthracite as in completely coked coke) not a 

 hydro-carbon, lu-ight, sooty flame, but the pale -blue 

 lambent flame of carbonic oxide gas, in the course of its 

 further combustion, i.e., a gas consisting of one equiva- 

 lent of carbon, combined with one of oxygen, taking up 

 an additional equivalent of oxygen, represented in 

 chemical symbols as CO-f becoming CO.,. 



Most of my readers are fn,miliar with the ph}\sical 

 characters of anthracite : its hardness, its lustrous black- 

 ness, and the fact that, when free from dust, it does not 

 stain the fingei's as ordinary bituminous coal does. This 

 is due to its compact and homogeneous structure, as •well 

 as to its havduess. Common coal is a medley of lr,mini3e, 

 or layer.i of vegetable niR.teriil, cf different degrees of 

 hardnes.^ r.ud varying structure, some portions being 

 friable to the touch of the fiager.~. 



It should be observed that no broad natural line can be 

 drawn between bitiiminous coal and anthracite. Soft 

 bituminous caking coal contains as much as 35 or 36 per 

 cent, of volatile hydro-carbons. This is the case^ or 

 rather was the case, with the famous " Wallsend coal," 

 now practically exhausted. Other seams of bituminous 

 coal similarly rich in the bitumen constituents exist. 

 They are usually soft, and become semi-fused or pasty 

 when heated, throwing out jets of gas, which push before 

 them the pasty coal in rounded projecting craters, and 

 leaving a very porous coke. I once had considerable 

 trouble in making an experimental distillation of a ten- 

 ton sami>le of a remarkable coal of this sort from the 

 neighbourhood of Ruabon, and known there as the " Wall 

 and bench " seam. My retorts, specially constructed for 

 obtaining liquid products from cannel and shale, were 

 long iron chambers, with doors at both ends. The coal 

 was charged in trays that entered at the cooler end, and 

 were pushed forwards down the slojiing chamber to the 

 hottest or firing end, and there withdrawn on to trollies, 

 one out at this end, and one in at the other. The " Wall 

 and bench " coal swelled like bakers' dough, and jammed 

 all the trays so firmly, that their release was p. serious 

 business. 



My own analysis of twelve different kinds of ordinary 

 medium or rather hard coals used at the Atlas Iron Works, 

 Sheffield, and from as many different collieries in the 

 neighbourhood, show a range from 24 per cent. (" Staveley 

 Hard ") to 29 per cent. ('' Stone's Soft "), and an average 

 of 2t)'2 per cent, and an average of 4'27 per cent, of 

 water and ammonia in adtlition. 



From such coal as this there is decline, without break, 

 to the hard coals of South Wales, used in the iron-works, 

 containing but 20 per cent. n,nd thereabouts of hydro- 

 carbons. In this district a very interesting and instruc- 

 tive gradation occurs. On the eastern extremity of the 

 seam the coal is bituminous, fairly rich in hydro-carbons; 

 proceeding westwards it becomes the harder p,nd uemi- 

 bituminous " steam coal" ; onward and westward it pro- 

 ceeds with diminishing volatile constituents until it 

 becomes true anthracite. The same gr.idation has been 

 observed in the coal-seams of the Alleghany Mountains of 

 North America ; in the great Eussian coal-field lying 

 between the Dnieper and the Don, north of the Sea of 

 Azof, which has an area of about 11,000 square miles; 

 and in other places. 



The difference between cannel coal and ordinary bitu- 

 minous coal is by no means so simple or so easily explained 

 as that between anthracite and bituminous coal. Some 

 of the cannels contain more Tolatile matter than the 



softest of the soft bituminous coal, but are nevertheless 

 very hard. Besides this, the composition of their in- 

 flammable volatile constituents is different. They afe 

 hydro-carbons, but belong to quite a different series, with 

 different properties as illuminants. The subject is inte- 

 resting, and has not received the attention it deserves. I 

 will discuss it in mj- next. 



THE STORY OF CREATION, 



A PLAIN ACCOUNT OF EVOLUTION. 



Br EriwiED Clodd. 



II. — The Stuff of which the Universe is made up. 



IE Universe is made up of Matter, Force, 

 and Energy. 



I. Matter, under which term is com- 

 prised all substances that occupy space 

 and affect the senses, is manifest in three 

 states, solid, liquid, and gaseous. It is 

 probably also present throughout the 

 universe in the highly tenuous form called ether. 



Between the above three states there is no absolute 

 break, matter assuming any one of them according to the 

 relative strength of the forces which bind and of the 

 energies which loosen the component parts of bodies ; 

 in other words, according to the temperature or pressure ; 

 e.g., water becomes solid when its latent heat or contained 

 motion is dissipated, and gaseous to invisibility when 

 its particles are driven asunder by heat. 



Since the ultimate nature of matter remains unknown 

 and unknowable, we can only infer what it is by learning 

 what it does. The actions of bodies, whatever their 

 states, are explicable only on the assumption that they 

 are made up of infinitely small particles which, in their 

 combined state as mechanical units, are called molecules ; 

 and in their free state, as chemical units, are called atoms, 

 or elementary bodies. The molecule, which is a com- 

 pound body reduced to a limit that cannot be passed 

 without altering its nature, can be divided : the atom 

 cannot, whence its name (Greek atomos, indivisible). 

 E.g., common salt, the chemical name (>f which is 

 chloride of sodium, has its molecule made up of the 

 combined atoms chlorine and sodium ; water is made 

 up of atoms of hydrogen and oxygen ; plants and 

 animals mainly of atoms of carbon, oxygen, hydrogen, 

 and nitrogen. 



The atoms or elementary substances number, so far as 

 is known at present, about seventy, but many of them are 

 extremely rare, and exist in such minute quantities as to 

 be familiar only to the chemist. Perhajs we may one 

 day find that the larger number are compounds, perhaj s 

 that there is one element ; but the labours of many years 

 have as yet brought us no nearer their decomposition. 

 They are the raw stuff of which the universe is built, 

 and however much they may vary in their distribution 

 and their combinations, each one is unchangeable in its 

 properties, and withal indestructible. It matters not into 

 how many myriad substances — animal, plant, or mineral 

 — an atom of oxygen may have entered, neither what 

 isolation it has undergone : bond or free, it retains its own 

 qualities. It matters not how many millions of years 

 have elapsed during these changes, age cannot wither or 

 weaken it ; amidst all the tierce play of the mighty forces 

 to which it has been subjected, it remains unbroken and 

 unworn — to it we may apply the ancient words, " the 

 things which are not seen are eternal." 



