r 3 * 7 1 
XXL Experiments and Obferv.atio.ns to invefigate the Cowpojitiom 
of James’s Pozvder. By George Pearfon, M. D . F. R . S.y, 
communicated by Sir Jofeph Banks, Bart . P. P. -S'. 
Read June 23, 1791* 
T HE medicine upon which many phyficians principally' 
depend in the cure of continued fevers is James’s Pow- 
der ; but, although it has been very extenfively ufed above 
thirty years, the public have not, I believe, been informed 
of the particular nature of this fubftance, This powder was 
originally a patent medicine ; but it is well known that it can- 
not be prepared by following the dire&ions of the fpecification 
in the Court of Chancery. Prefuming that 1 have made feme 
experiments and obfervations which may explain the nature 
and manner of preparing this medicine, and, perhaps, may 
extend the hiftory of antimony ; I beg leave to have the honour 
of prefenting an account of them to the Royal Society.. 
Senfble properties of James’s Powder . 
Some parcels of this preparation are white, but in general It 
has a yellowifh caft ; and this fhade is more evident in fome 
fpecimens than in others. It is faid, that this powder cannot, 
in general, be made at. different times of precifely the fame 
fhade of yellow or degree of whitenefs. Sometimes with the 
aid of a lens a few very fmall fhining fpicula are feen mixed 
with powder. When preffed between the fingers it feels 
fmoothy 
