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XVIII. Observations and Experiments upon Dr. James’s Powder ; 
with a Method of preparing , in the humid Way , a similar Sub- 
stance. By Richard Chenevix, Esq. F. R. S. M. R. I. A. 
Read June 4, 1801, 
After the observations and experiments made by Dr. Pearson, 
to investigate the nature of Dr. James’s Powder, and presented 
by him to this Society, very little remained to be effected or 
desired, towards a further knowledge of the subject. But those 
very experiments served to suggest, that the mode of prepara- 
tion was far from being the best that the present improved state 
of chymical knowledge might afford ; and that, in all probabi- 
lity, a less defective composition might result from a process 
more conformable to some improvements, which of late have 
been advantageously applied to pharmaceutic chymistry. 
It may be laid down as a general principle, that, in delicate 
experiments, whether analytical or synthetical, fire (that potent 
and once believed to be universal agent) is too precarious in its 
means, and too uncertain in its application, to be employed with 
full and constant success. And, if it is still recurred to, the 
advantage of promptness, and a remnant of ancient custom, 
are the principal reasons.. But, where other methods can be de- 
vised to effect the same combinations, (and the humid way offers 
many,) every person conversant in chymical knowledge will al- 
low the benefit of adopting them, The recent improvement in 
