201 
found in the ruins of Herculaneum. 
the membrane was attached, and then to begin with a very 
slight increase of temperature ; as otherwise, by too sudden 
an application of heat, the membrane shrivelled before it be- 
came adherent, and the vapour suddenly raised destroyed its 
union with the papyrus; whereas, when the moisture was suf- 
fered to drain from the gelatinized glue, and the temperature 
was gradually raised, the expansion of the skin and the upper 
layer separated them perfectly from the lower layers, so that 
the unrolling was performed, as it were, by chemical means ; 
and an operation, which hitherto had required some hours for 
its completion, was easily effected in from 30 to 40 minutes. 
I tried several experiments, by substituting solution of 
resins in alcohol and of gums in water for the gelatinized 
solution ; but none of them answered so well ; the resins 
would not adhere with any tenacity to the membrane, and 
the gums, when dried, had not that flexibility, which is an 
important character in the glue. 
The alterations in the mode of applying and drying the 
membrane used to detach and preserve the leaves of MSS. 
capable of being unrolled, applied generally ; I shall now 
mention the plans I adopted for the preparation of the MSS, 
for this operation. 
MSS. in different states required a treatment of a directly 
opposite kind, which was to be modified according to circum- 
stances. The pale chesnut-coloured MSS., covered partially 
with white ashes, were generally of a texture so loose, and 
had their layers so destroyed, that there was considerable 
danger of their falling into pieces by mere touching. The 
characters that remained in many of them were extremely 
distinct; and when a number of layers were taken up at 
