( 17P4 ) 
11. Obferyations on Jlninin^ the Fingers with a Solution 
of Siher m Aqua Fortis, &cc. In a Letter from 
' Mr Anthony Van Leuwenhoek, .F. (^, 5. 
Delft in HoOa^d^ March 3. 1705. 
SEveral Months ago, I took 24 Ounces of mixt Metal, 
and put the fame into Aqua Fortff, and fet it on Warm 
Sandj and there being a fault in the Glafs, it crackt 5 by 
which fome of the Aqna Fortis^ which was impregnated 
with Silver, run into the Sand, and I don't know but I 
might have loft Gold, alfo in the fame. This Sand, as 
niuch of it as was wet, I got together, and tho' 1 took 
all the care imaginable, that the v/et Sand (hould not 
ftick to my Fingers, yet I faw the tips of them were 
ftain'd, that I could fee a difcolouring of the Skin with 
my naked Eye 5 and as this happen'd in the Evening I 
waftit my Hands in common Water, and I faw the next 
day, that the tips of moft of my Fingers were black. 
I then took, according to the Surgeon s rnftruftions, 
fome frefli Butter to get the blacknefs off of my Hands 
and Fingers,but how hard foever I rubb'd them with the 
faid Butter, yet I could not fo much as ftir the blacknefs 5 
To then I took fome Soap, but all in vain. I rubfa'd my 
Thumb on a Grtndftone with Water and Sand, which 
leflen'd the blacknefs a little, but did not take it quite off. 
The third day, looking very attentively upon my black 
Fingers, 1 refolv'd to cut off feme thin Scales of the Skin, 
aud to fee if I could get any Silver out of it, fo as to be 
able to perceive that it was Silver. I cut off fome fmall 
pieces 
