Franklin ya lura da ka'idar sanyaya ta hanyar lura da cewa a ranar da yake da zafi sosai, ya kasance mai sanyaya a cikin rigar rigar rigar a cikin iska mai iska fiye da yadda ya yi a cikin bushe. Don fahimtar wannan abin da ya faru Franklin ya gudanar da gwaje-gwaje. A 1758 a rana mai zafi a Cambridge, Ingila, Franklin da abokin aikinsa masanin kimiyya John Hadley sunyi gwaji ta hanyar ci gaba da yin amfani da kwalliyar ma'aunin zafi na Mercury tare da ether da kuma amfani da bellows don busa ether. Tare da kowane ɓoyewa na gaba, ma'aunin zafi ya karanta ƙananan zafin jiki, daga bisani ya kai 7 ° F (-14 ° C). Wani ma'aunin zafi ya nuna cewa zafin jiki na ɗaki yana ci gaba da kasancewa a 65 ° F (18 ° C). A cikin wasikarsa ta Evaporation Cooling, Franklin ya lura cewa, "Mutum na iya ganin yiwuwar daskarewa ga mutum har ya mutu a ranar zafi ta rani". Tambaya: Menene masanin kimiyya John Hadley yayi a shekara tare da wetting ball na ma'aunin zafi na Mercury?
1758 da kuma