Cooling by rapid expansion had actually been established earlier in 1852 by James Prescott Joule and William Thompson (later Lord Kelvin) as the Joule-Thompson effect. Using this effect in a closed cycle mode, Carl Paul Gottfried von Linde patented and installed in Munich a commercial refrigeration system in 1873. Now, apparently, only hydrogen was left to liquefy. William Ramsay, in University College London, isolated helium (earlier discovered spectroscopically in the Sun) while looking for Argon. He got the Nobel prize in 1904 for his discovery of He, Ne, Ar, Kr, Xe. In 1877, Sir James Dewar became Fullerian Professor of chemistry (a chair earlier held by Faraday) at the Royal Institution. He obtained a Cailletet apparatus and started his work liquefying gases. produced solid oxygen in 1886. He wanted his work/demo to be visible to the public while giving a talk etc. therefore wanted to have transparent vessels but then there is a problem of thermal isolation. He invented the double walled dewar for this purpose. On 10 May 1898 Dewar produced 20 cc of liq H2. He deduced a temp of 20.28 K, eventually even solidified H2 at 14 K. helim still remained. Dewar and Ramsay would have been a great pair to liquefy helium but they had a falling out. Ramsay announced to the Royal Society that in fact Dewar was not the first to liq H but that it had already been done by Prof. Olszewski from Poland. It turned out that he was wrong and even Olszewski admitted that Dewar was first!