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peculiar odour, resembling that of empyreuma, or of bitumen. In 

 this state it is generally known by the term mow-burnt hay. But if 

 the process be allowed to go on, the heat soon considerably aug- 

 ments, the vapour assumes the form of smoke, and, at length, 

 actual flames break forth, and the whole mass is presently reduced 

 to ashes. 



The remarkable evolution of heat, in the fermentation I have just 

 spoken of, demands an inquiry whether any thing similar ever takes 

 place in the process of bituminization ; since, if that be not the 

 case, the parallel would so far fail. But, as the process of bitumi- 

 nization is carried on out of the reach of our examination, it is 

 impossible, as has been already observed, to speak accurately re- 

 vspecting the phenomena which arise during its performance. The fol- 

 lowing account, however, contained in a letter from Peter Collinson, 

 Esq. to Sir Hans Sloane, which I met with among the unprinted 

 papers of the Royal Society, preserved in the British Museum, shows 

 that tliis phenomenon may arise during this process. You will also 

 perceive that the learned writer proposed to account for its occur- 

 rence in a similar manner with that which I have here adopted. 



" Our newspapers, printed here, mention the burning of Brooks, 

 in the Vale of Good Cheap; but the case is, that some pieces of 

 marshy ground, called brooks, from their watery situation, have 

 flamed for some time; and these they have called burning brooks; 

 the parish next adjoining is also called Brooks. The soil is like 

 those parts of Cambridgeshire, where the turf is cut, and very often 

 under water ; but this dry season has brought it from very wet to 

 that degree of moisture which often causes hay to ferment and 

 take fire. Accordingly, this fire begins about four feet underground, 

 just above the water (as appears by digging), and so burns up to 

 the surface, where it flames out, especially if stirred with any thing ; 

 and, according to the quantity of .roots and fuel it meets with, it 

 leaves strata of black coal, or red ashes. The fire has now burnt. 



VOL. i. c c 



