Any sportsperson who ever sipped hot coffee from a thermos while sitting in a duck blind or deer stand on a cold morning can thank British chemist Sir James Dewar. Dewar worked with liquid gases and needed to keep them at a constant temperature. In 1892 he invented the vacuum flask, or, as we know it today, the thermos bottle. I don't know if Sir James was a sportsman, but he sure did the rest of us a great service for more than a hundred years now with his invention. The modern stainless-steel thermos is one of the least expensive yet most valuable pieces of equipment the outdoorsman has. Except for washing, it requires no maintenance and is as indestructible as a manhole cover.