Although he was insulted by Lord Rayleigh when he questioned Rayleigh's discovery of argon, Dewar was highly regarded by scientists 100 years ago.

In 1880, he performed an experiment which showed that a pressure of 77 Mpa (megapascal) was needed to keep water from freezing at -5 °C.
On an ordinary day, air pressure is 0.1 Mpa

In 1892, to store liquid air which boils at -180 °C, he invented the "Dewar flask". This was a double walled glass vessel with an evacuated space between the walls. The thermos is the modern descendant.

He investigated surface phenomena and kept a soap bubble "up" for three years.

This is the structure he proposed for benzene. It is quite unlike the Kekule structure.
Today with the benefit of spectroscopic studies we know this compound as bicyclo[2-2-0] hexadiene. If it is heated at 90 °C for 30 minutes it is converted into benzene.