b. 10 December 1874 Providence, Rhode Island, USA
d. 9 December 1974 Providence, Rhode Island, USA
After obtaining BSc and MSc degrees in physics at Brown University in 1896 and 1897, respectively, Cady went to Berlin, obtaining his PhD in 1900. Returning to the USA he initially worked for the US Coast and Geodetic Survey, but in 1902 he took up a post at the Wesleyan University, Connecticut, remaining as Professor of Physics from 1907 until his retirement in 1946. During the First World War he became interested in piezo-electricity as a result of attending a meeting on techniques for detecting submarines, and after the war he continued to work on the use of piezo-electricity as a transducer for generating sonar beams. In the process he discovered that piezo-electric materials, such as quartz, exhibited high-stability electrical resonance, and in 1921 he produced the first working piezo-electric resonator. This idea was subsequently taken up by George Washington Pierce and others, resulting in very stable oscillators and narrow-band filters that are widely used in the 1990s in radio communications, electronic clocks and watches.
Internationally known for his work, Cady retired from his professorship in 1946, but he continued to work for the US Navy. From 1951 to 1955 he was a consultant and research associate at the California Institute of Technology, after which he returned to Providence to continue research at Brown, filing his last patent (one of over fifty) at the age of 93 years.
President, Institute of Radio Engineers 1932. London Physical Society Duddell Medal. Institute of Electrical and Electronics Engineers Morris N. Liebmann Memorial Prize 1928.
b. c.57 AD China
d. c.121 AD China
He was a confidential secretary to the Emperor. He became Director of the Imperial Workshops and he is said to have invented, or sponsored the invention of, paper around the year 105 AD. Recent studies, however, suggest that paper was already known in China two centuries earlier. The method of making it has hardly varied in principle since that time. The raw materials, then usually old fishing nets and clothing rags, were boiled with water, to which alkali in the form of wood ash was sometimes added. The resulting pulp was then beaten in a stone mortar with a stone or a wooden mallet. The pulp was then mixed and stirred with a large amount of water, and a sieve or mould (formed on a wooden frame carrying a mat of thin reeds sewn together) was dipped into it and was shaken to help the fibres in the layer of pulp to interlock and thus form a sheet of paper. The rest of the process consisted, then as now, of getting rid of the water: the sheets of paper were dried and bleached by leaving them to lie in the sun.
Some of China's many inventions were achieved independently in Western Europe, but it seems that Europe's knowledge of papermaking stems from the Chinese. It was not until the eighth century that it passed into the Islamic