Reflecting on heat

Marc-Auguste Pictet was a Swiss editor of the Bibliothèque Britannique, a publication that shared scientific knowledge developed in Great Britain with a continental audience. In addition to his journalism, Pictet carried out his own scientific studies. In one experiment, the report of which was published in 1790, he arranged two tin mirrors 3 m apart and placed a thermometer and a ‘matrass full of snow’ at their respective foci. He reported that as soon as the ‘matrass’ was in place, the temperature recorded on the thermometer began to fall. Pictet found that he could cause a greater fall in temperature by pouring nitric acid on the snow. He reported that, “The act was notorious, and amazed me at first; this phenomenon offered nothing more than a final proof; if it had been necessary, of the reflection of heat...”. The phenomenon would be now be described as the result of the reflection (or lack of reflection) of infra-red radiation.