Q. What is the principle involved in hydraulic jacks?
A. A pump operated by hand forces a small amount of alcohol through a narrow valve into a recess containing a ram or large piston-rod. As the alcohol is forced into this recess it raises the ram: thus a weight upon the ram-head is raised. The alcohol is prevented from running back into the main reservoir by valves similar to those on all pumps.
Q. What is the best liquid to use in filling jacks?
A. For the base jack one part alcohol, two parts water; for the horizontal jack one part alcohol, one part water, and for both add a tablespoonful of sperm-oil.
Q. Name the principal parts of a jack.
A. The cylinder, ram, reservoir, socket, knuckle, piston, piston-valve, pump, pump-valve, lowering-valve, packing-springs, etc. (See Figs. 52 and 53.)
BASE JACK.