F66 SHALES AND MINERAL OILS 



wider stratigraphical knowledge has made the two terms synonymous. Haculloch, in 

 his ' Classification of Rocks,' has shown that a shale may leave the fissile state to pass 

 in the same geological section into the botryoi'dal, mammillary, and even earthy con- 

 ditions. There are arenaceous, argillaceous, calcareous, or ferruginous shales, accor- 

 ding to the nature of the parent-rock ; thus, red haematite and the organically-derived 

 Tripoli slate may be both included under the generic term. Use in manufactures 

 has given names to alum-shales, argillo- or calcareo-bituminous, or, better still, oil- 

 shales. 



Like petroleum, oil-shales are found in all geological formations, and they appear 

 to accompany both it and limestone geognostically. Wherever fossils indicate con- 

 ditions of quiet subsidence, and estuary or lake formation, the observer has come on a 

 locality, primd facie, good for the occurrence of either oil-shales or petroleum. Sueb 

 conditions in geography appear to have alternated with those of a sudden change to 

 deep-sea life throughout all geological time. The Scottish carboniferous system 

 appears to have been formed under very favourable circumstances for the production 

 of oil-producing materials. The Mountain Limestone, instead of attaining the mag- 

 nificent proportions of Derbyshire or Northumberland, is represented usually by six 

 thin beds of a few feet thick. The reader, casting his eye on a geological map of 

 midland Scotland, will mark how comparatively small a space is occupied by the coal- 

 fields proper ; that they are, in fact, surrounded by a large area of beds marked off in 

 the books as the subcarboniferous or estuarine Burdiehouse-limestone formation. 

 This, the area proper of the shales, extends through the counties of Fife, Edinburgh, 

 Linlithgow, Lanark, Renfrew, and Ayr. But the true coal-formation also abounds in 

 oil-producing material. Very intimately associated with each individual coal-bed, the 

 occurrence of shale above it, and blackband ironstone below it, also an oil-yielder, 

 may possibly indicate a different mode of formation from that of the Newcastle field. 

 The rich cannels found throughout the Scotch coal-fields proper belong to the category 

 of shales rather than coals. 



During the years immediately succeeding the expiry of James Young's patent, oil- 

 works were erected over the area of the Scottish coal-field. But since the continued 

 depression of this new industry caused by the large importation of American petroleum, 

 many small works have been dismantled ; and the trade is now principally in the 

 hands of a few large companies, who carry on their operations near West Calder and 

 Broxburn, in the immediate neighbourhood of Edinburgh, and in the vicinity of Paisley. 

 The amount of material used is still very great. The Addiewell works are alone 

 capable of utilising 1,000 tons of shale weekly. So much as 782,000 tons of shale 

 have been consumed annually ; resulting in the manufacture of about 10,000,000 

 gallons of burning-oil, 5,000 tons of paraffin, and about 600 tons of sulphate of 

 ammonia. 



The Torbanehill mineral, the substance on which Young worked his patent, is now 

 exhausted. But the high price given for it by foreign gas-companies, as well as the 

 demand from the same quarters for the ordinary cannels, and for the bastard cannel, 

 technically termed ' rums,' which abound throughout the Scotch coal-fields, have placed 

 all these substances out of the reach of the oil-maker. The shales of the lower fresh- 

 water series were waste products before the advent of this new industry ; but from 

 their special chemical nature, they yield an oil more easily brought to the white standard 

 in colour of American petroleum than the substances first employed in the manufac- 

 ture of crude oil. 



The probable organic origin of a shale or cannel. The Kimmeridge shale yielded an 

 oil which could not be deodorised. So though a newly-discovered Brora shale yields 

 as much as 57 gallons to the ton, it may probably be used only for the purposes of 

 patent fuel, owing to the phosphorus it contains, derived from the animals whose re- 

 mains are in part chemically represented by its oleaginous contents. So also of 

 abundant flagstone bituminous beds of the Old Red Sandstone of Orkney and the North 

 of Scotland. The same difficulty has been experienced with the Canadian petroleum ; 

 though it is said that in this special material the art of the refiner has overcome the 

 disagreeable odour. 



The close proximity of coal and shale, often found in one section, is of great 

 importance in diminishing the working expenses of a shale oil-work. In Scotland, 

 oil-makers generally also mine their raw products. 



What is a Coal'! A strict chemical definition of coal or its allies has as yet been 

 attempted in vain. Use has hitherto ruled the distinguishing nomenclature of coals. 

 From the anthracite to the cannel, a clear gradation may be traced. But here we 

 reach a once much contested border-land, where the true cannel graduates into the 

 shale. The advocates of separation of the celebrated Torbanehill mineral from the 

 class of cannel coals mainly contested that, unlike these bodies, after the oil or gas 

 had been taken from them, it left no useful coke containing an appreciable percentage 



