Mechanical Appliances. 323
and may be carted away. Or a sledge may be built beneath the mass by burrowing below it and thrusting the poles beneath it. Then the remainder of the intervening sand can be shovelled away, and the mass, now resting directly upon the sledge, can be dragged away by a team of cattle.
A sarcophagus of immense weight was raised from out of a deep recess into which it had been fitted pretty closely, at the end of a long narrow gallery in an Egyptian tomb, where there was no room for the application of tackle or other machinery, by the simple expedient of slightly disturbing it in its place and sifting sand into the narrow interval between its sides and the recess. This process was repeated continually : the sand settled below the bottom of the sarcophagus, which gradually rose out of the hole in which it had lain. The principle of this piece of engineering was borrowed, I suppose, from observing that whenever a mass of sand and stones is shaken together, the stones invariably rise out of the sand, the biggest of them always forming the highest layer.
Expansive Power of Wetted Seeds.-Admiral Sir E. Belcher read a curious paper before the British Association in 1866, showing the remarkable power to be obtained by filling tubes with peas or other seed, allowing the weight to rest upon the surface of the peas through the medium of a rude piston. When the peas were wetted they swelled upwards with considerable force. A pint of peas placed in a tube of a diameter that was not expressed in the newspaper report, from which I take this account, lifted 60 lbs. through a height of one inch in twenty-four hours. The Admiral proposed to fix a number of tubes side by side in a frame below the mass to be lifted, preferring to use zinc tubes of from two or three inches in diameter, and of about one foot high. Thus, in the small space of a cubic foot, a large number of tubes (thirty-six in the one case, sixteen in the other) could be made to act simultaneously ; the force of the stroke could be increased by arranging a number of frames side by side, or the length of the stroke could be increased by building the frames in a series one above the other. I have elsewhere described how wetted seeds may be used to restore the shape of a battered flask either for holding water or gunpowder (pp. 230, 244).