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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link="#0563C1" vlink="#954F72"><div class=WordSection1><p class=quotation><span class=mw-headline><span style='font-style:normal'>Nocturnal ice making in early India and Iran</span></span><o:p></o:p></p><p class=quotation>In India before the invention of artificial refrigeration technology, ice making by nocturnal cooling was common. The apparatus consisted of a shallow ceramic tray with a thin layer of water, placed outdoors with a clear exposure to the night sky. The bottom and sides were insulated with a thick layer of hay. On a clear night the water would lose heat by radiation upwards. Provided the air was calm and not too far above freezing, heat gain from the surrounding air by <a href="https://en.wikipedia.org/wiki/Convection" title=Convection><span style='font-style:normal'>convection</span></a> was low enough to allow the water to freeze.<sup id="cite_ref-icemaking_radiative_5-0"><a href="https://en.wikipedia.org/wiki/Radiative_cooling#cite_note-icemaking_radiative-5"><span style='font-style:normal'>[5]</span></a></sup> A similar technique was used in Iran as well.<sup id="cite_ref-6"><a href="https://en.wikipedia.org/wiki/Radiative_cooling#cite_note-6"><span style='font-style:normal'>[6]</span></a></sup> <o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>I confused the issue by insisting that the dish be a parabola. <o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Nick <o:p></o:p></p><p class=MsoNormal>Nicholas Thompson<o:p></o:p></p><p class=MsoNormal>Emeritus Professor of Ethology and Psychology<o:p></o:p></p><p class=MsoNormal>Clark University<o:p></o:p></p><p class=MsoNormal><a href="mailto:ThompNickSon2@gmail.com">ThompNickSon2@gmail.com</a><o:p></o:p></p><p class=MsoNormal><a href="https://wordpress.clarku.edu/nthompson/">https://wordpress.clarku.edu/nthompson/</a><o:p></o:p></p><p class=MsoNormal> <o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p></div></body></html>