Water-bag

[…] he went off alone with his family, and, watched by the day's red baleful eye, pumped the pump-car homeward, pausing at the summit of every bank to drink with greed from the water-bag and nurse his head.

Before long we had, willy-nilly, to replenish the water in our radiator from our water-bag, a canvas sack holding a few quarts, in which, thanks to evaporation through the canvas, the water remains cool even on the hottest day.