65 



towards the roof of the cavern, I observed a black patch vertically 

 above the heap of supposed soot lying on the floor, and from 20 to 

 30 feet above it. The dotted line, a b, fig. 5, may repre- 

 sent the position. 



On my return from the cavern I examined* the black sooty matter* 

 and found that it left but very small traces under the action of the 

 blowpipe. 



On the following day, having made inquiries as to the drainage of 

 the neighbouring country, I was informed that about twenty years 

 before my visit, a stream of water had been diverted from the valley 

 in which it originally flowed, into another adjacent valley. 



I then visited several quarries, in one of which, about a mile from 

 the caves, I observed a small stream of water terminating in a little 

 pool or sink. In this pool I noticed slight eddies, which occasionally 

 sucked in very small particles floating on the surface of the water. 



I now visited the valley from which the original stream had been 

 diverted, and found at some elevation a peat bog to which it had pro- 

 bably given rise. This peat was in several parts nearly black ; the most 

 decayed portion greatly resembled the black matter I had brought 

 from the cavern. The origin of this black matter in the cavern now 

 became apparent. 



The large caverns I had visited were considerably below the level 

 of the peat moss, and the stream which flowed through it. A portion 

 of its waters was conveyed by sinks and crevices into the caves, and 

 kept them continually full. There must, however, have been some 

 very small leakage through which, when the stream which supplied 

 the water was cut off, those caverns were, after many years, laid dry. 



A small mass of unconsolidated peat, sufficiently light to float, 

 must have been conveyed by the water into those caverns. When 

 it arrived at the spot on which the black matter was found, the 

 piece of peat which still floated must have been pressed against the 

 roof of the cavern. Remaining there undisturbed for years, it may 

 have become by decomposition specifically heavier than water, and 

 then have subsided vertically down on the floor to the place on which 

 I found it, leaving in the black spot on the roof the certificate of its 

 former residence. On the other hand, the piece of peat may have 

 retained its power of floating, and only have descended to the floor 

 of the cavern by the slow escape of the water. 



VOL. x. F 



