C 638 ] 
ther, I {hall endeavour to procure them fubfcribers to 
their work, and lhew them every civility in my 
power. 
LXXXVI. Experimental Examination of 
a white metallic Subjlance / aid to he found 
in the Gold Mines of the Spanifh Weft- 
Indies, and there known by the Appella- 
tions of Platina, Platina di Pinto, Juan 
Blanca. By William Lewis, M. B. 
F. R. S. 
PAPER I. 
Read May 30, 1 754. 
Experment 1. 
T H E fubftance brought into England under the 
name of platina appears a mixture of diffimilar 
particles. 
The moft confpicuous, and by far the largeft part 
of the mixt, are, white, fhining grains, of feemingly 
fmooth furfaces, irregular figures, generally planes 
with the edges rounded off. Upon examining thefe 
with a microfcope, the furface appear’d in fome parts 
irregular i the prominencies fmooth, bright, and 
fhining j the cavities dark-colour’d and roughifh. A 
few of them were attracted, tho’ weakly, by a mag- 
netic bar. 
The grains above defcrib’d are the true platina. 
The heterogeneous matters intermingled among them, 
in the feveral parcels, were, 
1. A 
