Induction Balance
a modification of the microphone. Its object is to measure the differences in the molecular constitution of metallic bodies. A milligram of copper on an iron wire finer than the human hair has been detected, and its exact value ascertained, by this delicate instrument. In its present form it consists of two flat coils, about 4 inches in diameter and 1/2 inch in thickness, of INDULIN insulated copper wire, battery, condenser, circuit and telephone.