Who invented the first thermos flask?

Sir James Dewar, in the year 1892. It consists of a double-walled flask with a vacuum between the walls. The walls are silvered and heat cannot be conducted across a vacuum. They keep hot liquids hot because the heat cannot get out and cold liquids cold because heat cannot get in. After the liquid has been poured in, a cork stopper is used to seal the flask as cork is a very poor conductor of heat.