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Experiments and Observations in a Heated Room (1774)


“Experiments and Observations in an Heated Room” by Charles Blagden, in Philosophical Transactions (1683-1775); 1775; Royal Society, London.

In 1774 and 1775 the British physician and scientist Charles Blagden conducted a series of experiments concerned with exploring the effects on the human body of extremely high temperatures, “air heated to a much higher degree than it was formerly thought any living creature could bear”. In what equated to something akin to a “super-sauna”, Blagden and his co-experimenters (including a dog) subjected themselves to enormously hot temperatures. Beginning at a modest 100 degrees Fahrenheit (38 degrees Celsius), by the 1775 session they progressed to temperatures upward of a whopping 260 degrees Fahrenheit (127 degrees Celsius). Not surprisingly the air was at times quite literally scorching, and a full cladding of clothing was mostly worn to protect their skin, though Blagden did experiment one time being in the room naked from the waist up with only a suspended cloth protecting him from the rays of the hot irons. Among his many observations, in his latter 1775 report to the Royal Society, Blagden became the first to explicitly recognise the role of perspiration in thermoregulation, seeing that the body temperatures of both the heat-subjected humans and heat-subjected dog were significantly lower than the air they were exposed to. The dog endured a temperature of 236 degrees Fahrenheit (113 degrees Celsius) for a full hour, with seemingly little distress, and recording a body temperature of only 110 Fahrenheit (43 degrees Celsius) – higher than a dog’s normal body temperature, but significantly cooler than the room. In reality the dog’s temperature was probably lower by a few degrees, as Blagden acknowledged he had a bit of trouble taking the measurement. In any case, such a difference in body and room temperature was an important one. Fearing the reliability of his thermometers, Blagden thought up a control for this thermo-regulating tendency of living bodies which he’d observed – a fat juicy steak. As he explained in his Royal Society report:

To prove that there was no fallacy in the degree of heat shewn by the thermometer, but that the air which we breathed was capable of producing all the well-known effects of such an heat on inanimate matter, we put some eggs and a beef-steak upon a tin frame, placed near the standard thermometer, and farther distant from the cockle than from the wall of the room. In about twenty minutes the eggs were taken out, roasted quite hard; and in forty-seven minutes the steak was not only dressed, but almost dry. Another beef-steak was rather overdone in thirty-three minutes. In the evening, when the heat was still greater, we laid a third beef-steak in the same place : and as it had now been observed, that the effect of the heated air was much increased by putting it in motion, we blew upon the steak with a pair of bellows, which produced a visible change on its surface, and seemed to hasten the dressing; the greatest part of it was found pretty well done in thirteen minutes.

(For more self-experimentation in the name of science see the Nitrous Oxide experiments of Humphry Davy)

Housed at: Internet Archive (1774) & (1775) | From: The Royal Society
Underlying Work: PD Worldwide | Digital Copy: No Additional Rights
Download: PDF, (1774) & (1775)