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 in a due proportion of water, would very considerably infrigidate it; as may further appear by the Notes, which for your greater satisfaction you will find here subjoyn'd, as soon as I have told you, that, though for want of other vessels I was first reduc'd to make use of Earthen ones, and the rather, because some Metallin Vessels will be injur'd by the dissolv'd Sal Armoniack, if it be boyl'd in them; yet I afterwards found some conveniencies in Vessels of other Mettall, as of Iron; whereof you may command a further Account.