^ Analt/ses of Books, [Jan. 



in an atmosphere of chlorine, and the letters became much 

 more distinct ; the vapour of iodine had a sensible, but less 

 distinct action. 



In using chlorine it was found necessary to employ only a 

 small quantity of it, and when the temperature was properly 

 regulated, the muriatic acid vapour formed assisted the sepa- 

 ration of the leaves. 



The number of MSS. found at Herculaneum was stated to 

 Sir H. Davy to be originally 169G; of these about one-fourth 

 had been operated on or presented to foreign governments ; and 

 on inspecting the state of those which remained, it did not ap- 

 pear that more than from 80 to 120 offered proper subjects for 

 experiments; and this estimate afterwards appeared too high. 



feir Humphry remarks that the persons to whom the care of 

 the MSS. is confided, or who have worked upon them, have 

 always attributed the appearances which they possess to the 

 action of fire, more or less intense ; but he is of opinion that 

 the operation of fire is not at all necessary for producing such an 

 imperfect carbonization of vegetable matter as that displayed by 

 the MSS. and he strengthens his opinion by observing, that at 

 Pompeii, which was covered by a shower of ashes that must have 

 been cold, as they fell at a distance of seven or eight miles from 

 the crater of Vesuvius, the wood of the houses is uniformly con- 

 verted into charcoal ; yet the colours on the walls, most of which 

 would have been destroyed or altered by heat, are perfectly 

 fresh, and where papyri. have been found, they have appeared in 

 the form of white ashes, as of burnt paper. 



Sir H. concludes, that the difiisrent states of the MSS. 

 depend upon a gradual process of decomposition, by the action 

 of air and water ; the results of the action of heat upon the 

 different specimens of the papyri proved hkewise that they had 

 never before been exposed to any considerable degree of temper- 

 ature. 



Only one method, and that a very simple mechanical one, had 

 been used for unrolling the MSS. It consisted in attaching 

 thin animal membrane by a solution of glue to the back of the 

 MSS. and carefully elevating the layers by silk threads when the 

 glue is dry. This, however, was found to be attended with 

 some inconvenience, which Sir H. Davy proposed to obviate by 

 mixing the glue with sufficient alcohol to gelatinize it : in this 

 mode, the alcohol, from its greater hghtness, penetrated further 

 into the papyrus, but produced its greatest effect immediately on 

 the first layers. Ether was also tried by Sir H. Davy, and found 

 to be efficacious ; it was applied by a camel's hair brush, with 

 precautions, for which we must refer our readers to the paper, as 

 well as for other experiments. 



For some time. Sir H. Davy states, that he was at liberty to 

 choose and operate upon specimens ; but even after the efficacy 

 and use of the new processes were fully allowed by the unrollers 



