DI′APHRAGM

(frăm). A partition through or acro ; a dividing substance. In anatomy , the term is applied to the midriff, a muscle separating the chest or thorax from the abdomen or lower belly. In astronomy and optics the term is applied to a circular ring placed in a telescope or other instrument to cut off the marginal portions of a beam of light. In electricity the name is commonly used to denote the porous partition, cell, or ve el, that separates the fluid containing the positive plate from the fluid which surrounds the negative plate, in a constant voltaic battery. Thin partitions of sycamore, or other porous wood, are occasionally used, but cells made of thin biscuit ware are the most convenient and durable diaphragms. Plaster of Paris, animal membrane, coarse and tightly wove canvas, ., are used also for the purpose. Plaster cells are also formed by surrounding an oiled cylinder of wood with a hoop of paper, and pouring plaster of Paris, mixed up with water, into the space between the two. See Electrotype .