He had heard that creatures substantially larger than the dinosaurs of ancient Earth could not exist on land. On an Earth type planet, which this one was with regard to gravity, atmosphere and climate, the limits were not so much biological as physical. A diminutive insect required many legs, not to support its weight, but to preserve balance. Brontosaurus, with legs many times as sturdy as those of an insect, even in proportion to its size, had to seek the swamp to ease the overbearing weight. A larger animal, in order to walk at all, would have to have disproportionately larger legs and feet. Mass cubed with increasing size while the cross section of the legs squared; to maintain a feasible ratio, most of the mass above a certain point would have to go to the feet.
Four hundred and sixty tons? The weight on each foot exceeded that of a family of whales. Bones should shatter and flesh tear free with every step.
The rain had ceased and the forest was quiet now. Tinnerman scraped up a belated bed of his own and lay down. But his mind refused to be pacified. Bright and clear and ominous the thoughts paraded, posing questions for which he had no answer. What thing had they blundered across?
A jumping animal! Tinnerman sat up, too excited to sleep. Like an overgrown snowshoe rabbit, he thought—bounding high, hundreds of feet to nip the lofty greenery, then landing with terrific impact. It could be quite small—less than a ton, perhaps, with one grossly splayed balancing foot. At night it might sail into a selected roost ... or onto....
He turned his eyes up to the impenetrable canopy above. In the flattened upper reaches of the banyan ... a nest?
Tinnerman stood, moving silently away from the bodies of his companions. Locating his pack a second time he dug out cleats and hand spikes, fitting them to his body by feel. He found his trunk, shaping its firm curvature with both hands; then he began to ascent.
He climbed, digging the spikes into the heavy bark and gaining altitude in the blackness. The surface gradually became softer, more even, but remained firm; if it were to pull away from the inner wood the fall would kill him. He felt the curvature increase and knew that the diameter of the trunk was shrinking; but still there was no light at all.
His muscles tensed as his body seemed to become heavier, more precariously exposed. Something was pulling him away from the trunk, weakening his purchase; but he could not yet circle any major portion of the column with his arms. Something was wrong; he would have to descend before being torn loose.
Relief washed over him as he realized the nature of the problem. He was near the top; the stem was bending in to join the main body of the tree, and he was on the underside. He worked his way to the outside and the strain eased; now gravity was pulling him into the trunk, helping him instead of leaving him hanging. Quickly he completed the ascent and stood at last against the massive nexus where limb melded into bole.