Experiments on heat His experiments on gunnery and explosives led to an interest in heat. He devised a method for measuring the
specific heat of a solid substance but was disappointed when
Johan Wilcke published his parallel discovery first. Thompson next investigated the
insulating properties of various materials, including
fur,
wool and
feathers. He correctly deduced that the insulating properties of these natural materials arise from the fact that they inhibit the
convection of air. He then inferred — incorrectly — that air and, in fact, all gases, were perfect non-
conductors of heat. He further saw this as evidence of the
argument from design, contending that
divine providence had arranged for fur on animals in such a way as to guarantee their comfort. In 1797, he extended his claim about non-conductivity to liquids. The idea raised considerable objections from the scientific establishment,
John Dalton and
John Leslie making particularly forthright attacks. Instrumentation far exceeding anything available in terms of accuracy and precision would have been needed to verify Thompson's claim. Again, he seems to have been influenced by his theological beliefs, and historian of science
D. S. L. Cardwell speculated that Thompson wished to grant water a privileged and providential status in the regulation of human life. He is considered the founder of the
sous-vide food preparation method owing to his experiment with a mutton shoulder. He described this method in one of his essays.
Mechanical equivalent of heat Rumford's most important scientific work took place in Munich, and centred on the nature of heat, which he contended in "
An Inquiry Concerning the Source of the Heat Which Is Excited by Friction" (1798) was not the
caloric of then-current scientific thinking but a form of
motion. Rumford had observed the frictional heat generated by boring cannon at the arsenal in Munich. Rumford immersed a cannon barrel in water and arranged for a specially blunted boring tool. He showed that the water could be boiled within roughly two and a half hours and that the supply of frictional heat was seemingly inexhaustible. Rumford confirmed that no physical change had taken place in the material of the cannon by comparing the specific heats of the material machined away and that remaining. Rumford argued that the seemingly indefinite generation of heat was incompatible with the caloric theory. He contended that the only thing communicated to the barrel was motion. Rumford made no attempt to further quantify the heat generated or to measure the mechanical equivalent of heat. Though this work met with a hostile reception, it was subsequently important in establishing the laws of
conservation of energy later in the 19th century.
Calorific and frigorific radiation He explained
Pictet's experiment, which demonstrates the reflection of cold, by supposing that all bodies emit invisible rays, undulations in the ethereal fluid. He did experiments to support his theories of calorific and frigorific radiation and said the communication of heat was the net effect of calorific (hot) rays and frigorific (cold) rays and the rays emitted by the object. When an object absorbs radiation from a warmer object (calorific rays) its temperature rises, and when it absorbs radiation from a colder object (frigorific rays) its temperature falls. See note 8, "An enquiry concerning the nature of heat and the mode of its communication" Philosophical Transactions of the Royal Society, starting at page 112.
Inventions and design improvements Thompson was an active and prolific inventor, developing improvements for chimneys, fireplaces and industrial furnaces, as well as inventing a
double boiler, a
kitchen range, and a
coffee drip-press pot roughly between 1810 and 1814. He invented a percolating coffee pot following his pioneering work with the Bavarian Army, where he improved the diet of the soldiers (
Rumford's Soup) as well as their clothes. The
Rumford fireplace created a sensation in London when he introduced the idea of restricting the chimney opening to increase the updraught, which was a much more efficient way to heat a room than earlier fireplaces. He and his workers modified fireplaces by inserting bricks into the hearth to make the side walls angled, and added a choke to the chimney to increase the speed of air going up the flue. The effect was to produce a streamlined air flow, so all the smoke would go up into the chimney rather than lingering and entering the room. It also had the effect of increasing the efficiency of the fire, and gave extra control of the rate of combustion of the fuel, whether wood or
coal. Many fashionable London houses were modified to his instructions, and became smoke-free. Thompson became a celebrity when news of his success spread. His work was also very profitable, and much imitated when he published his analysis of the way chimneys worked. In many ways, he was similar to
Benjamin Franklin, who also invented a new kind of heating stove. The retention of heat was a recurring theme in his work, as he is also credited with the invention of
thermal underwear.
Industrial furnaces , with the fuel chamber at the left Thompson also significantly improved the design of kilns used to produce
quicklime, and
Rumford furnaces were soon being constructed throughout Europe. The key innovation involved separating the burning fuel from the limestone, so that the lime produced by the heat of the furnace was not contaminated by ash from the fire.
Light and photometry Rumford worked in
photometry, the measurement of light. He made a photometer and introduced the
standard candle, the predecessor of the
candela, as a unit of
luminous intensity. His standard candle was made from the oil of a sperm whale, to rigid specifications. He also published studies of "illusory" or subjective complementary colours, induced by the shadows created by two lights, one white and one coloured; these observations were cited and generalized by
Michel-Eugène Chevreul as his "law of simultaneous colour contrast" in 1839. ==Later life==