that continued a considerable while
unthaw'd away, and was in some places about the thickness of a half Crown
piece.

Another Observation, made the same Spring, but less solemn, as meant
chiefly to shew the Duration of Cold in a high degree, is recorded in these
terms: The first time, the Seal'd Weather-glass was put in, before it
touch'd the common water, it stood at 8-1/8, having been left there a
considerable while, and once or twice agitated the water, the tincted
liquor sunk but to 7-7/8, or at furthest, 7-6/8; then the frigorifick
liquor being put into the water with circumstances disadvantagious enough
in (about) half a quarter of an hour the tincted liquor fell beneath 33/4,
and the Thermoscope, being taken out, and then put in again, an hour after
the water had been first infrigidated subsided beneath 5 inches, and
consequently within 1/4 of an inch of the mark of the strongly freezing
weather.

7. Whereas the grand thing, that is like to keep this Experiment from being
as generally _Useful_, as perhaps it will prove _Luciferous_, is the
Dearness of Sal Armoniack, two things may be offered to lessen this
Inconvenience. For _first_, Sal Armoniack might be made much cheaper, if
instead of fetching it beyond-sea, our Country-men made it here at home;
(which it may easily be and I am ready to give you the Receipt, which is no
great Secret.) But _next_, I considered, that probably the infrigidating
vertue of our mixture might depend upon the peculiar Texture of the Sal
Armoniack whereby, whilest the Water is dissolving it, either some
Frigorifick particles are extricated and excited or (rather) some particles
which did before more agitate the minute parts of the water, are expell'd
(or invited out by the ambient Bodies) or {261} come to be clogg'd in their
motion: Whence it seem'd reasonable to expect that upon the Reunion of the
Saline particles into such a Body, as they had constituted before, the
redintegrated Sal Armoniack having, neer upon, the same Texture, would,
upon its being redissolv'd, produce the same, or a not much inferior degree
of Coldness: And hereupon, though I well enough foresaw that an Armoniack
solution, being boyl'd up in Earthen vessels (for Glass ones are too
chargeable) would, by piercing them, both lose some of the more subtle
parts, and thereby somewhat impaire the texture of the rest; yet I was not
deceiv'd in Expecting, that the dry Salt, remaining in the pipkins, being
redissolv'd i