{2416 ) 
V. An Extratt of a Letter to his Excel- 
lency Signior Francifco Cornaro, Am- 
bafjador from the Republick of Venice, 
to the Queen of Great Britain, &c. By 
Anthony Van Leeuwenhoek, F.R.S. 
Containing Microfcopical Obfervations of 
the Salts of Pearls, Oyfter-ihells, &c. 
I Thought it my Duty to teftifie my Thankfulnefs by 
thefe tew Lines, and therewith to join home of my 
poor Obfervations, &c. 
Pearls are prefcribed as a very wholfomeMedicine upon 
divers occafions,to all thofe that are able to pay for them. 
Now in order to make a Trial of the fuppofed Ver- 
tues of Pearls , I took feven little ones, all which being 
laid in a row together, did not exceed the length of an 
Inch. Then I put them upon a Silver-Smiths Charcoal 
Fire, and made them Red-hot after which I threw them 
into clean RainWater, which caufed them immediately 
to burft in pieces ; whereupon I took the Pearls and 
put them into a Glafs Tube, and placed the Tube and 
Pearls over fuch a fharp Fire that they were both Red- 
hot. Upon the burftiag of the Pearls there arofe a 
Smoke, and there was alfo a yellowilh Oyl drawn of 
from them. 
Thofe Oily Particles ftuck upon the fides of the Glafs 
in divers places, and were divided into fuch exceeding 
fmall Globules, that feveral Thoufands of them toge- 
ther did not amount to the .bignels of a fingle Grain of 
Sand ; but in other places the Particles of Oyl were 
coagulated into much larger Figures. When 
