René-Antoine Ferchault de Réaumur

French naturalist

• Born: February 28, 1683; La Rochelle, France
• Died: October 17 or 18, 1757; near Saint-Julien-du-Terroux, France

Réaumur markedly improved metallurgical technology in France and performed groundbreaking experiments involving limb regeneration in crustaceans. As a result of his observations of insects, he is considered by some to be the founder of animal-behavior studies.

Primary fields: Biology; chemistry

Specialties: Ecology; zoology; metallurgy

Early Life

René-Antoine Ferchault de Réaumur was born on February 28, 1683, in La Rochelle, a small city on the west coast of France. His family, the Ferchaults, came from a life of commerce, and they entered the ranks of the lesser nobility when they purchased the Réaumur estate. Réaumur’s father, who died in 1684, was in the legal profession. Réaumur’s early education was most likely with the Jesuits. In 1699, he traveled to Bourges, in central France, to study civil law.

There is no indication that Réaumur’s education included any substantial study of science or mathematics until 1703, when he settled in Paris and studied with Guisnée, a mathematician about whom little is known. Réaumur seems to have shown great aptitude for mathematics, and he subsequently furthered his education with Pierre Varignon, who taught him mathematics and physics, two subjects that were to influence Réaumur’s later work. Varignon nominated Réaumur for membership in the French Academy of Sciences, an institution founded by Louis XIV to promote scientific research. Réaumur became a member of the academy in 1708 and remained involved with it for the rest of his life.

Réaumur continued to study mathematics until 1709, presenting such promising work to the academy that Varignon thought he would go on to achieve great things in the subject. However, mathematics was not to be the field in which Réaumur would make his contribution to the sciences. In 1709, he read and disagreed with a paper on the growth of mollusk shells, a fateful event that precipitated a shift in his studies and marked the beginning of his lifelong interest in natural history.

Life’s Work

Despite his early training in mathematics, Réaumur devoted the majority of his life to other subjects, including metallurgy and natural history. In the early years of the eighteenth century, the French Academy of Sciences wanted to produce an encyclopedia of industry, and it was Réaumur who took on the project, a fact that might explain the diversity of his scientific studies in the decade following his admission to the academy.

The eclectic subjects that occupied Réaumur from 1710 to 1712 included determining that mollusk shells grow through accretion, rather than expansion; obtaining dye from mollusk shells; investigating the commercial potential of spider silk; and, most important, experimenting with the regeneration of crustacean limbs. Réaumur’s work with crustaceans set him apart as a scientist because he created a highly controlled laboratory setting in which he could observe what happened when he cut off the legs of crayfish. At the time, the ability of crayfish to regenerate limbs was considered something of an old wives’ tale, but through careful documentation, Réaumur proved the tale true.

Beginning in 1713, Réaumur focused primarily on the encyclopedia, and therefore on matters of technology instead of biology. Ironwork and the making of steel had long been practiced, but the field of metallurgy had not advanced particularly far. Réaumur set about studying iron, steel, and other metals, recording the way they fractured and examining the particles and patterns of fractured surfaces. He linked the patterns he observed to methods and speeds of cooling and connected the pattern and shape of the grain to the properties of the metal. Because iron castings were too hard to be worked, Réaumur began to experiment with methods of making them malleable. He noticed that when placed in a fire, iron develops a layer of oxides, beneath which it is soft; therefore, he intensified the process, deliberately adding oxides to cast iron before heating. He also developed a process to coat iron or steel with tin to render it less vulnerable to rust.

For the most part, the years following Réaumur’s metallurgical work were dominated by his natural-history studies, but one of his final contributions to the field of technology was the invention of the thermometric scale known as the Réaumur scale. The thermometer used alcohol and an eighty-degree scale, with the freezing point of water set to zero and the boiling point set to eighty. The thermometer attempted to eliminate accuracy problems with the Fahrenheit scale, but it had other issues and was used in France for only a short time, roughly from the 1730s until the adoption of the Celsius scale in 1794.

During the 1730s and 1740s, Réaumur’s worked on his proposed ten-volume Mémoires pour servir à l’histoire des insects (Memoirs to illustrate the history of insects, 1734–42). Only six volumes of the workwere completed in Réaumur’s lifetime, but they contain several groundbreaking studies. Perhaps the most significant is in volume two, which addresses the influence of temperature on the life cycle and development of insects. Réaumur went about exploring this question with his usual thoroughness, keeping pupae in warm and cool conditions and noting the moths’ emergence times. Using these observations, he was able to estimate population increases under different conditions. Réaumur also included the impact of parasites and predators on butterfly populations, studying how population increases are controlled and how weather conditions affect both predator and prey.

Volume five of Réaumur’s Mémoires focuses on bees and flies. His work with bees is particularly noteworthy because he began to delve into the manner in which bees communicate, something that had not been researched before. Methodically, Réaumur tracked individual bees, dissected them and discovered parasites inside them, recorded hibernation temperatures, and elucidated the function of the queen and how the hive responded when she was taken away or when new queens were introduced. In essence, he documented every aspect of bee biology that he could. The seventh volume of Mémoires was never finished, but the partial manuscript includes documentation of Réaumur’s observations of ant diet and hibernation patterns, ant-aphid interactions, mating biology, and ant predation of flowers of fruit trees.

Réaumur’s scientific work consumed his life, and he never married or had a family. The exact date of his death is not known; he died on either October 17 or 18, 1757, of injuries sustained after falling from his horse.

Impact

In the eighteenth century, tools such as the microscope had not long been in existence and were not as powerful as they would become. Therefore, little was known about the chemistry or molecular structure of metals. For this and other reasons, France was lagging far behind in the field of metalwork. Thus, Réaumur’s studies, particularly his method of creating malleable iron, were tremendously important to advancing French industry.

While Réaumur is not famous for any particular discovery or theory, he had a profound influence on his contemporaries and the scientists who came after him. His methods of observation and experimentation, particularly with regard to regeneration and insect behavior, were unique and groundbreaking, doing much to improve the ways animals were studied.

Réaumur was notable for nurturing the work of other scientists, particularly at the start of their careers. When his observations of aphids led him to conclude that only female aphids existed, he invited others to continue his work in case he was in error. This led to Swiss naturalist Charles Bonnet discovering parthenogenesis in aphids.

Throughout his life, Réaumur was constantly involved with the French Academy of Sciences, serving as either its director or its subdirector, influencing the course of the sciences and technology in France for the span of four decades during a time of immense change and innovation. In this and other ways, he fostered the scientific community. He was incredibly forward thinking in his encouragement of the sharing of research, specimens, and knowledge.

Bibliography

Egerton, Frank N. “A History of the Ecological Sciences, Part 21: Réaumur and His History of Insects.” Bulletin of the Ecological Society of America 87.3 (2006): 212–24. Print. Focuses on Réaumur’s entomological studies, putting them in the context of the work of his contemporaries and paying particular attention to how he influenced other naturalists. Extensive bibliography.

James, Ioan Mackenzie. Remarkable Biologists: From Ray to Hamilton. New York: Cambridge UP, 2009. Print. Provides a solid biographical background and situates Réaumur’s work by profiling the scientists who came before and after him, creating a chronology of ideas and influence.

Ratcliff, Marc J. “Experimentation, Communication, and Patronage: A Perspective on René-Antoine Ferchault de Réaumur (1683–1757).” Biology of the Cell 97.4 (2005): 231–33. Print. Discusses Réaumur’s scientific method, his encouragement of the sharing of information and specimens, and how he helped create a scientific culture that had a lasting impact on other scientists.

Smith, Cyril Stanley. A History of Metallography: The Development of Ideas on the Structure of Metals before 1890. Chicago: U of Chicago P, 1960. Print. Focuses solely on Réaumur as an innovator in metallurgy, discussing both the importance of his scientific method and his impact on French industry. Illustrations.