We place several different shapes of single loops of copper wire inside a long solenoid that is about 45 inches long and six inches in diameter. One of the loops is merely a rectangular loop of wire whose plane can be made to lie on the midplane of the solenoid. Other loops consist of circles or semicircles that are perpendicular to the axis of the solenoid. The leads from these loops come out either close together or widely separated. The loops are made in this fashion so that they represent paths of the line integral ∫ E dl. The solenoid has three layers of wire in parallel and can be used with either one or all of these layers. The changing field is produced by shorting out the ends of the coil with a General Electric relay-operated vacuum switch. The rate of change of the magnetic field within the coil can thus be calculated from the known and measurable constants of the solenoid. The emf developed in the various loops is displayed on a storage oscilloscope so that one can measure the peak emf and the time constant of the decaying field in the solenoid. With a constant voltage across the solenoid, the peak emf is independent of the number of layers, whereas the time constant will vary as the resistance is changed. In this arrangement the oscilloscope requires sensitivities of one or two millivolts/cm.