156 THE BURXIKG CLIFF AT LYME REGIS. 



the combination of the sulphide of iron with oxygen from the air 

 to form sulphates, some oxide of iron and sulphurous acid gas 

 being also formed. It is a well-known chemical fact that heat is 

 always developed when oxidation occurs, and that when the pro- 

 cess is rapid, the temperature sometimes rises high enough to 

 produce actual combustion. 



In this particular case it is clear that circumstances were 

 specially favourable to combustion. Iron-pyrites is abundant in 

 the shales from which the mound came ; the whole mass was 

 loose and saturated with the winter rains which helped the 

 decomposition of the pyrites. Again, the dark colour of the 

 shales indicates the presence of much organic matter, and INIr. 

 Cameron informs me that some of them are sufficiently bitu- 

 minous to ignite after pieces have been thoroughly dried in a 

 kitchen oven. It is not surprising, therefore, that spontaneous 

 combustion should have taken place in a heap of such 

 materials. 



When smoke began to issue from this mound, it must have 

 presented some resemblance to a volcano, and the combustion 

 continued more or less vigorously from January to June, without 

 any other change taking place. ^Ir. Cameron relates that on 

 the morning of June loth, he and the Vicar of Lyme Regis 

 were on the ground close to the burning-mound, which was 

 smoking as usual ; but about half- past one on that day he was 

 told that " the volcano had burst," and on going down he found 

 that a landslip had taken place, and that the mound had been 

 split in two by a fissure, so that its interior was exposed, looking 

 like the inside of a brick-kiln, from the baked appearance of the 

 shale and stone. 



3. The Landslip. 



The landslip took place about 1.15 p.m. on June loth. As 

 above stated, Mr. Cameron was on the cliffs about an hour before 

 it happened, and he did not notice any signs of an impending 

 change. No new fissures had appeared, and no mo^"ement was 



