Jan. 1, 1886.] 



KNOWLEDGE ♦ 



79 



carbons, the most volatile or gaseous and least complex of 

 which is Methane, CHj ; the second is the Benzine series 

 starting in like manner from benzine, CnH„. Having 

 promised at the outset not to mystify the non-technical 

 reader by an unintelligible display of my own technical 

 erudition — (a proceeding as easy as grinding a barrel- 

 organ when one has a text-book at hand), I will simply 

 add that the various distallates from cannel, — whether 

 they be gaseous at ordinary temperatures ; or volatile 

 liquids like the miscalled " benzoline " used in sponge- 

 lamps ; or less volatile liquids siich as common paraffin 

 oil and lubricating oil ; or solids like the material of 

 paraffin candles — all contain fewer equivalents or atoms of 

 carbon than of hydrogen, and all of those similarly 

 obtained by the distillation of ordinary bituminous coal 

 contain equal or excessive equivalents of carbon. In 

 consequence of this the paraiEn or cannel series bums with 

 a whiter, more luminous, and less smoky flame under 

 ordinary conditions than the series from ordinary coal. 

 Cannel gas properly made and burnt in a suitable burner 

 has about double the illuminating power of ordinary coal 

 gas. 



The superior value of cannel gas is shown by the 

 following figures, which I take from Clegg's " Treatise on 

 Coal Gas." A cubic foot of gas from Newcastle Coking 

 Coal (Pelton Main) burnt in a small batswing burner gave 

 an amount of light equal to 232 grains of sperm, with an 

 Argaud burner 311. Newcastle cannel gas gave an 

 average of 606. This double value is of great import- 

 ance to the consumer, as the heat and the mischievous 

 products of combustion are foot for foot about equal in 

 both cases. With unmixed cannel gas, one burner gives as 

 much light as two of ordinary gas. Corporations that 

 are sufficiently civilized to make their own gas, give the 

 benefit of this to the consumer ; but we poor company- 

 ridden cockneys are supplied with gas as bad as the Act 

 of Parliament permits, and thus have to bum a larger 

 quantity and pay our tyrants accordingly. 



At the time when I commenced distilling coal and 

 shale, it was generally stated on the authority of 

 Reichenbach, that the production of the paraffin series 

 depended on the low temperature of distillation. 

 The claim in Young's patent was based upon this 

 assumption, and the celebrated case of Young & 

 Fernio was decided accordingly. I soon discovered, 

 however, and others similarly engaged did the 

 same, that this was quite wrong ; that whatever be 

 the temperature of distillation in either case, each kind 

 of coal pi'odiiced its own distinct hydro-carbon series : 

 that by no mere variation of temperature could bituminous 

 coal be made to yield the marsh gas or paraffin series, nor 

 by any such variation could the cannel coal, or the black 

 shale associated with it, be made to yield the benzine 

 series or napthalene. Variations of temperature affected 

 the specific gravity and volatility of the products — i.e., 

 the proportions of the difl'erent members of the series, 

 but did not convert one series into the other. I state 

 this with especial emphasis, because it is still but 

 doubtfully understood by laboratory chemists, though 

 clear enough to gas-makers and shale-distillers i and 

 further and more particularly because it has an important 

 and unrecognised bearing upon the whole theory of the 

 formation of coal. 



The theoretical question it raises is this. Does the 

 existing vegetable kingdom present us with any great 

 class or classes of plants that yield upon distillation a 

 hydro-carbon series corresponding to that obtained from 

 cannel coal ; and is there any other class or classes that 

 yield a series similar to that obtained from ordinary 



bituminous coal ? If so, we are justified in referring their 

 origin to such classes respectively. 



Everybody knows that the tar used by sailors has a 

 near physical resemblance to ordinary coal-tar, and that 

 it burns with a similar smoky flame ; the chemist recog- 

 nises a similar close resemblance, though not an absoltite 

 identity. The tar and pitch used on board ship are ob- 

 tained by distilling coniferous plants, pines, larches, firs, 

 &c. Turpentine and resin are also obtained. Turpen- 

 tine, resin, " Stockholm tar," and pitch are a family series, 

 varying in boiling-]5oints or volatility. They dift'er only 

 slightly in their chemical composition from the series 

 obtained from similar distillation of ordinary bituminous 

 coal, and this difference is just such as exposure to oxida- 

 tion, or, more especially, to the action of water, will 

 effect. 



My chemical readers will understand the force of this 

 when I remind them of the fact that tei-ebenthene, 

 CioH,6, the type of the turpentine and resin series, is 

 readily converted by the action of bromine and iodine 

 into cymene, C]„H,4, a typical member of the benzene or 

 coal-tar series, and that similar acids are obtained by the 

 oxidation of both series. 



The camphors distilled from laurels and the naphthas 

 from most of our forest trees have a similar close 

 resemblance to the coal-tar series, but they all stand apart 

 and keep apart from the marsh-gas, or paraffin series, 

 obtained by the distillation of cannel. 



Does any existing vegetation produce this last-named 

 series ? I am able to reply to this question, having dis- 

 tilled compressed peat in substantial quantities (one 

 sample amounted to twenty tons), in the same retorts as 

 were used for cannel. Excepting that the proportion of 

 ammonia was much greater from the peat and the hydro- 

 carbons very scanty, the results were the same ; the 

 hydro-carbons were distinctly of the paraffin series, and, 

 when refined, were undistinguishable from the cannel 

 products. In the crude state, their aroma was somewhat 

 different. 



Peat is made up of defunct mosses, cryptogamous or 

 non-flowering plants. Here, then, we have a clearly 

 defined and rather broad distinction. I am not prepared 

 to assert that all the cryptogamia will yield the same 

 results on distillation, my experiments on other members 

 of this great subdivision of the vegetable kingdom being 

 too limited for this : but they go far enough to justify 

 further investigation. 



The evidence supplied by the marsh gas itself points in 

 the same direction. The vegetation of marshes is chiefly 

 cryptogamic, and the gas is due to a slow distillation of 

 the remains of such vegetation. 



These facts obviously suggest the hypothesis that 

 cannel deposits are ancient and fossilised peat bogs, while 

 ordinary bituminous coal is the material of ancient 

 forests. The idea that coal seams generally are ancient 

 peat bogs much consolidated by pressure is an old one 

 that has been much discussed, but the above-stated 

 chemical facts indicate pretty clearly that we must be 

 cautious in accepting any sweeping generalisation that 

 applies alike to the formation of all coal. We must re- 

 memember that both cannel and ordinary coal are found 

 in the same coal-fields, though usually separated by 

 mineral strata. The chemical differences, therefore, 

 cannot be due to differences of pressure or subterranean 

 temperature. A specifically different material must have 

 been originally deposited. 



Intimately associated with cannel are the bituminous 

 shales. All that I am acquainted with yield the same 

 products as cannel on distillation. There may be some 



