ALUM ,; 97 
fome Days, for in that Time it will have 
precipitated many Cry dal's to the Bottom, 
whereby the Liquor is fometimes left too 
weak for pur Purpofe ; but then, by holding 
the Phial over or near a Fire, the Cryflals 
will again diffolve, and be taken up a-new 
into the Fluid. 'Tis not however advife- 
able to make life of it as foon as this is done, 
unlefs we want to produce nothing elfe 
but Cryflals : for if, after this, it be em¬ 
ployed before it has had a little Time to 
cool and fettle, it is very apt to form into 
Cryflals only : but when it has flood about 
half an Hour, a Drop, placed on a Slip of 
Glafs and heated property, exhibits com¬ 
monly at the beginning a dark Cloud, which 
appears in Motion fomewhere near the 
Edge, and runs pretty fwiftly both to the 
Left and. Right, until it is either flopped 
by the Intervention of fome regular Cry- 
flals, or elfe proceeds onwards both Wavs 
at once, and nearly of the fame Height, 
till having furrounded the whole Drop the 
two Ends rufh together and join ; the Pro- 
grefs towards which is attempted to be 
fhewn, Plate III. N° I. a a. 
' This cloudy Part of the Drop, that feems 
violently agitated whilfl it is running round, 
appears on a flridl Examination to con fill of 
Salts, fhot into long and very flender Lines, 
much finer than the fmallefl Hair, which 
crofs one another at right Angles, and Form 
Vol. IL H ae 
