Helical

—Pertaining to or having the apfeat Unit.—1. Unit quantity of heat; the pearance of a helix or screw. amount of heat required to raise the temperature of a unit ma of water one degree. | Helical Coil. A coil of wire elongated 2. Tne British unit of heat, or British like the turns of a screw; a helix. thermal unit (B. T. U.) is that quantity of heat required to raise the temperature of one | Helical Spring.—A spring whose coils pound of pure water 1° Fahr., at or near 39.1° F have a gradually decreasing diameter, ' 3. The French heat unit or calorie is that quantity of heat required to raise the temperature of either lying flat in one plane like a watch one kilogramme of pure water 1° Centigrade, at spring, or a uming a conical form. The or about 4° C., which is equivalent to 39.1° F helical spring coiled on a cylinder is gener- One calorie = 3.968 B. T. U.; one B.T.U =.252 calorie. ally known as a spiral spring.