Passage: Franklin noted a principle of refrigeration by observing that on a very hot day, he stayed cooler in a wet shirt in a breeze than he did in a dry one. To understand this phenomenon more clearly Franklin conducted experiments. In 1758 on a warm day in Cambridge, England, Franklin and fellow scientist John Hadley experimented by continually wetting the ball of a mercury thermometer with ether and using bellows to evaporate the ether. With each subsequent evaporation, the thermometer read a lower temperature, eventually reaching 7 °F (−14 °C). Another thermometer showed that the room temperature was constant at 65 °F (18 °C). In his letter Cooling by Evaporation, Franklin noted that, "One may see the possibility of freezing a man to death on a warm summer's day."

Question: What was the temperature in Celsius during the experiment?
18 °C