burnt to that end before a more economical plan was discovered. As to the effect of fire on clay, Lord Avebury observes that clay-vessels may have been invented by (1) plastering gourds or coco-nuts with clay to resist the fire when boiling water in them; (2) observing the effect of fire on the clay; (3) leaving out the vegetable part.[12] This must have been a comparatively recent discovery; though there is some evidence of pottery having been made by palæolithic man. It is impossible to say when fire was discovered; but it was certainly known to the Mousterian culture—say, 50,000 years ago: probably very much earlier; and it was made by hunters.