( ) 
In the Ledures on DigefHon and Extra£Hon,he fhows 
that there is a Tenacity nn all Fluids, by which their FaVts 
do in fome mealure cohere together, and hinders their 
Effeds from being the fame as in a perfed Fiiiid. He 
gives us tl^e method of dtimating this Tenacity, and of 
finding out the proportion it may have to the weight of 
other Bodies *,■ and from thence he explains how fmall 
Particles of Matter, that are either fpecifically lighter or 
heavier than the Fluid, may be fulfained in it, which he 
explains by a Calculation ;„and fhows,thatif the Gravi- 
ty of the Body be to the Tenacity of the Fluid as P to i, 
if the Body be divided into Parts, wJiofe Diameters 
are to the Diameter of the whole as i to P, then thefe 
Bodies may be fulfained in the Fluid, tho* fpecifically 
lighter than themfelves. 
He obferves, that Tindurcs made by f^elfion are 
iifiially very ftrong, and faturated with the Body whofe 
Tindiire is extraded ; but if the Tindure‘'be di- 
ftilled in an Alembick, the Menlfruum generally rifcs 
with its former colour and dearnefs, leaving the Body 
behind it: The reafon of which he explains. * 
Heconfiders the feveral Preparations of Opium, and 
condemns fuch as are made, by the fumes of Sulphur, 
or by acid Liquors ; in which either the vertue of the 
Opium is loft, by the evaporatipn of its Volatile Parti- 
cles, or deftroyed by acid Salts, wliofe qualities are di- 
redly oppofite^to that of Opium ; the one coagulating 
or making* the Blood viicid, whereas the other attenu- 
. ates it, and rend^-rs :c fluid; But he approves of fudi 
Preparations of Opium cis are made witii hot and aro- 
ma tick ‘Medicines, which heighten its Vertue j. and 
feems.to prefer D,r. S/^;teds Preparation with Canary 
Wine to all others. . 
Precipitation, he fays, may be made byinfufing*a 
Liquor, that is' fpecifically ligiuer or heavier than tile 
Menftvuum; For by the firft the iEquilibrum that was 
between 
