Critical phenomena: 150 years since Cagniard de la Tour

Critical phenomena were discovered by Cagniard de la Tour in 1822, who died 150 years ago. In order to mark this anniversary, the context and the early history of his discovery is reviewed. We then follow with a brief sketch of the history of critical phenomena, indicating the main lines of development until the present date. Os fen\'omenos cr\'{\i}ticos foram descobertos pelo Cagniard de la Tour em Paris em 1822. Para comemorar os 150 anos da sua morte, o contexto e a hist\'oria initial da sua descoberta \'e contada. Conseguimos com uma descri\c{c}\~ao breve da hist\'oria dos fen\'emenos cr\'{\i}ticos, indicando as linhas principais do desenvolvimento at\'e o presente.Comment: Latex2e, 8 pp, 3 eps figures include

Thermal conductivity through the nineteenth century

As a material property and as a metaphor, thermal conductivity occupies an important position in physical, biological and geological sciences. Yet, its precise measurement is dependent on using electricity as a proxy because flowing heat cannot directly be measured.Comment: Submitted to Physics Today. 4,500 words, 4 figure

Secrecy, Industry and Science. French Glassmaking in the Eighteenth Century

Glass has always played a crucial role in directing the investigation of natural phenomena onto revolutionary and innovative paths. Since antiquity philosophers of nature perceived the peculiar quality of this material and their increasing attention to the extraordinarily rich and varied productions made by craftsmen after the introduction of glassblowing techniques reveal the special status glass had in the economy and culture of the Roman Empire. Because of its chemical nature, large scale production of glass was a difficult technological process which required, in addition to dexterity, a broad knowledge of different operations and devices. The fusion of glass requires high temperatures that can only be obtained with the construction of special furnaces and crucibles, combined with the accurate use of salts, namely soda and potash, which enables to decrease the degree of glass\u2019 fusion