562 Burning Clifs on the Mackenzie River. 



intervals to rise from, a mound on the edge of the cliffs, about half-way 

 between Lyme and Charmouth," and that the burning portion "con- 

 sisted of a large fallen mass of the cliff which had some time since 

 slipped away from the body of the cliff." Mr. A. C. G. Cameron, 

 who was at the time resident at Lyme Regis, explained that the case 

 was one of spontaneous combustion, due to the decomposition of iron 

 pyrites and the consequent generation of heat sufficient to ignite the 

 bituminous shales of the Lower Lias. 



Iron pyrites and marcasite (rhombic iron pyrites) are found more 

 especially in the Lias shales. They are most abundant in the shales 

 of the Lower Lias. At Black Ven, near Lyme Regis, there is 

 a 'Metal Bed,' and material derived from this and other layers was 

 formerly collected during the winter months for the preparation of 

 copperas (sulphate of iron), sulphuric acid, and sulphur. Examples 

 of marcasite from Lyme Regis are sold to visitors as ' angels' wings.' 



In August, 1751, spontaneous combustion occurred in the 

 bituminous shales of the Lower Lias near Charmouth.' This took 

 place among fallen masses of the strata, owing to the decomposition 

 of pyrites. In 1890 similar combustion took place further east, and 

 ia the Daily Graphic of February 19 there appeared a picture of 

 the * eruption ' of Golden Cap. 



In September, 1826, spontaneous combustion took place in the 

 Kimeridge Clay near the east extremity of Ringstead Bay, at Hoi worth 

 Cliff, adjacent to the promontory of Wliite Nore. This combustion 

 continued until 1829, although the extent of the surface of the clay 

 which was burnt did not exceed 50 feet square. 



Buckland and De la Beche state that " within this space are many 

 small fumaroles that exhale bituminous and sulphureous vapours, and 

 some of which are lined with a thin sublimation of sulphur ; much of 

 the shale near the central parts has undergone a perfect fusion, and is 

 converted to a cellular slag. In the parts adjacent to this ignited 

 portion of the cliff where the effect of the fire has been less intense, the 

 shale is simply baked and reduced to the condition of red tiles, like that 

 on the shore near Portland Ferry." '^ The occurrence of the burnt shale 

 at Portland Ferry indicates that there a similar combustion took place. 



Some of the above details are taken from the Geological Survey 

 Memoir on the Jurassic Rocks of Britain, vol. iii, p. 308, and 

 voL V, p. 331. 



H. B. W. 



VIII. — Burning Cliffs on the Banks of the Mackenzie River, etc. 



AS bearing upon the phenomenon of the spontaneous combustion 

 of bituminous beds of coaly or carbonaceous matter of any 

 geological age (charged with pyrites) m situ, the account given bj'- 

 Sir John Richardson, C.B., F.R.S., in his "Arctic Searching Expedi- 

 tion ; a Journal of a Boat-voyage through Rupert's Land and the 

 Arctic Sea," 1851, vol.i, may not be without interest in this connection. 

 He writes (p. 176): "On the Mackenzie a shaly formation makes 



' See J. Stephens, " An Account of an uncommon Phenomenon in Dorsetshire " : 

 Phil. Trans., vol. Iii, p. 119. 

 ^ Trans, Geol. Soc, ser. ii, vol. iv, p. 23. 



