Hiftory of Mining in Devon and Cornwall. 337 
acid: it therefore makes a chief component part of that pre- 
pared by Pitel, but it is mixed in it only mechanically. The 
following is a prefcription for preparing an ink of the like 
kind, but in which the indigo is actually diffolved. é 
Boil.1 oz. of Brazil waod, and 3 ozs. of coarfely pulverifed 
galls, with g ozs. of vinegar and as aeudh water, for the {pace 
of eight minutes: in the liquor, after being ftrained, diffolve 
1 0z. of fulphat of iron and 1 oz. of gum arabic, and'then 
add to the whole a folution of 1 0z. of indigo m I oz. of 
concentrated fulphuric acid. 
The oxy-muriatic acid diffolves the oxyd of iron in this 
ink, but the indigo remains undecompofed. The principal 
point to be attended to is, that the ink may contain fuch 
‘matters as are not affected by the oxy-muriatic acid: with 
other fubftances lefs deception is to be dreaded. 
In the laft place, I fhall mention an ink made with the 
principal ingredients of common ink, but in preparing 
which, inftead of the ufual liquids, I employed the exprefled 
juice of fome plant: the fitteft for this purpofe I found to 
be the leaves of the caper {purge, Euphorbia lathyris LInn.; 
the common holly, Sambucus niger, and common grafs. 
IX. Sketch artis Hiftory of Mining i in Devon and Cornwall, 
By Mr. Joun Taytor jun. Miner, Tavijlock. Commu- 
municated by the Author, 
a mutt be regretted that a fubje& of fo great national im- 
pertance, undertakings which engage fo large a capital, and 
give employment to fo many hands, as working the various 
mines in thefe kingdoms, fhould gain but little attention 
from any but thofe immediately concerned in them, and near 
the places in which they are fituated; it is the more to be 
_wifhed that men of fcience fhould devote fome thought to 
thefe concerns, as thofe, under whofe management moft of 
thefe works are carried on, are often not men of fufficient 
ability or feience to ftrike out capital improvements. To be 
a good miner requires an active mind, with induftry and 
rit obfervation; thefe fhould be accompanied by fome 
general 
