452 Dr. Blagden's O'jfervations on 
MSS. extended, was of the fame nature as the prefent : for 
the letters turned of a reddifh oryellowilh brown with alkalies, 
became pale, and were at length obliterated, with the dilute 
mineral acids, and the drop of acid liquor which had extradled 
a letter, changed to a deep blue or green on the addition of a 
drop of phlogifticated alkali ; moreover, the letters acquired a 
deeper tinge with the infufion of galls, in fome cafes more, in 
others lefs. Hence it is evident, that one of the ingredients 
was iron, which there is no realon to doubt was joined with 
the vitriolic acid ; and the colour of the more perfect MSS. 
which in fome was a deep black, and in others a purplifii black, 
together with the reftitution of that colour, in thofe which 
had loft it, by the infufion of galls, fufficiently proved that ano- 
ther of the ingredients was aftringent matter, which from 
hiftory appears to have been that of galls. No trace of a 
black pigment of any fort was difcovered, the drop of acid, 
which had completely extradted a letter, appearing of an uni- 
form pale ferrugineous colour, without an atom of black pow- 
der, or other extraneous matter, floating in it. 
As to the greater durability of the more ancient inks, it 
feemed, from what occurred to me in thefe experiments, to 
depend very much on a better preparation of the material upon 
which the writing was made, namely, the parchment or vel- 
lum ; the blacked: letters being generally thofe which had funk 
into it the deepeft. Some degree of effervefcence was com- 
monly to be perceived when the acids came in contact with the 
furfaceof thefe old vellums. I was led, however, tofufpedl, that 
the ancient inks contained a rather lefs proportion of iron than 
the more modern ; for in general the tinge of colour, produced 
by the phlogifticated alkali in the acid laid upon them, feemed 
lefs deep; which, however, might depend in part upon the 
6 length 
