1 42 Dr. Blagden’s Experiments on the 
nation. Water in freezing undergoes a confiderable expanfion. 
This may be afcribed to fuch a form of its particles, andpofi- 
tion of their poles, as fhall make them, when touching and 
adhering by thofe poles alone, intercept very large interflices, 
which may be confidered as the pores of the ice. Various por- 
tions of the poles and figures of the particles may be con- 
ceived, which fhould caufe them to occupy more fpace, when 
touching in certain points only, than they filled when lying 
near without any contaft. But in whatever way the expan- 
fion is produced, experiment hath ftiewn that it begins fome 
time before congelation ; fo that when water is cooled down 
to 32°, it is already fenfibly expanded; and if the congelation 
does not take place here, this expanfion augments, in pro- 
portion as the water is further cooled*. The expanfion, 
therefore, being fo evidently an approach to freezing, may 
be confidered as an indication that the polarity already pre- 
vails fo far as to draw the particles fomewhat out of the 
fituation they naturally aflame in the higher temperatures. And 
it is conceivable, that if this operation go on very quick, and 
the confequent change of pofition in the particles be made with 
fome degree of velocity, they may acquire a fmall momentum 
of motion, enabling them to overcome a refiftance which 
would otherwife prevent their junction. 
* In experiments where the water has cooled much below its freezing point, 
I have feen the expanfion fo great as to bear a confiderable proportion to the 
whole expanfion produced by freezing, which lafi, I believe, is more than one- 
feventh of the volume of the water. It feemed to me as if the expanfion proceeded 
in an increafing ratio, being much greater upon the lafi: degrees of cooling than it 
was upon the firft. The difficulty of procuring a proper apparatus for thefe experi- 
ments has hitherto prevented me from afcertaining the quantities withprecifion. 
As 
