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Chryftal is found to attra Gt a Corpufcle of Fire, if one 
of its Sides be turned towards the Chryftal, and repel it, 
if the other be; for one and the fame Ray is here 
refra&ed fometimes after the ufual, and fometimes 
after the unufual manner, according to the Pofition 
which its Sides have to the Chryftal 5 and fince the 
Chryftal, by this Difpofition or Virtue, does not a£t 
upon the Rays, unlefs when one of their Sides of 
unufual Refradion looks towards that Coaft, this argues 
a Virtue or Difpofition in thofe^Sides of the Rays, 
which anfwers to, and fympathizes with, that Virtue 
or Difpofition of the Chryftal, as the Poles of two 
Magnets anfwer to one another. 
XXVII; 
We are fully perfuaded, that, in the Chryftalliza- 
tion of Salts, they could not fo regularly and con- 
ftantly preferve their peculiar Shapes, Forms, and 
Figures, if every Particle of them had not its de- 
terminate Poles : For granting that the component 
Particles of each kind of Salt have a peculiar Shape 
and Size, different from any other kind of Salt, yet 
if they had a Power of uniting with each other 
indifferently, at their Tops, Sides, and Bottoms, 
one would think they could not always coalefce 
into Chryftals of the fame regular Figure : But if 
the conftituent Particles of every kind of Salt have 
their determinate Poles, then they cannot poffibly 
unite with each other, but when their Poles fquare 
with one another, and confequeiitly they will always 
fly together, and be joined at fuch Points, only where 
their correfponding Poles are j which muft of courfe 
conftantly produce the fame regular Form and Figure 
in 
