prairie was afterwards 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. § 3. MINOR AND SECONDARY CONSEQUENCES (1) The extensive adoption by Man of a flesh-diet many hundreds of thousands of years ago might be expected to have shortened his alimentary canal in comparison with that of the anthropoids; but not much evidence of it is obtainable. Topinard, giving a proportionate estimate, says that in Man it is about six times the length of the body, in the gibbon about eight times. Dr. Arthur Keith, in a private communication with which he has favoured me, says that the adult chimpanzee’s intestine is slightly longer than the adult man’s, but that the measurements are for certain reasons unsatisfactory, and that there have not been enough measurements of adult chimpanzees. We must remember that, on the one hand, the chimpanzee is not exclusively frugivorous, and that, on the other hand, it is not likely that Man has been at any time exclusively carnivorous; though the return of large populations to a vegetarian diet by means of agriculture is recent.