1 96 Sir Humphry Davy on the papyri 
presented leaves which separated from each other with 
considerable facility, and such had been for the most part ope- 
rated upon ; but in general the MSS. of this class were hard, 
heavy, and coherent, and contained fine volcanic dust within 
their folds. Some few of the black and darker brown MSS., 
which were loose in their texture, were almost entirely de- 
cayed, and exhibited on their surface a quantity of brown 
powder. 
The persons to whom the care of these MSS. is confided, 
or who have worked upon them, have always attributed these 
different appearances to the action of fire, more or less intense, 
according to the proximity of the lava, which has been ima- 
gined to have covered the part of the city in which they were 
found ; but this idea is entirely erroneous, that part of Her- 
culaneum being, as I satisfied myself by repeated examina- 
tions, under a bed of tufa formed of sand, volcanic ashes, 
stones, and dust, cemented by the operation of water (pro- 
bably at the time of its action in a boiling state). And there 
is great reason to conclude, that the different states of the 
MSS. depend upon a gradual process of decomposition : the 
loose chesnut ones probably not having been wetted, but 
merely changed by the re-action of their elements, assisted by 
the operation of a small quantity of air ; the black ones, which 
easily unroll, probably remained in a moist state without any 
percolation of water ; and the dense ones, containing earthy 
matter, had probably been acted on by warm water, which 
not only carried into the folds earthy matter suspended in it, 
but likewise dissolved the starch and gluten used in preparing 
the papyrus and the glue of the ink, and distributed them 
through the substance of the MSS., and some of these rolls 
