By using a barium titanate cylinder poled radially a lengthwise motion can be excited in the cylinder whose resonant frequency is controlled by the length of the cylinder. By using a 4 percent lead titanate‐barium titanate combination, stresses up to 1000 pounds per square inch of cross‐sectional dimension and motions up to 50 parts in 106times the length of the cylinder are available for static or slowly varying voltages of 15,000 volts per centimeter along the radial dimension. When such a cylinder is driven at its resonant frequency, the maximum strain appears to be limited to 10−4by heating considerations if no cooling is used. For a cylinder 12 centimeters long, which resonates at 18 kilocycles, this corresponds to a displacement on each end of 3.9 × 10−4cm, a particle velocity of 44 cm/sec and an acceleration of 5 × 10−6cm/sec/sec. All of these quantities can be enhanced by a factor of 10 by soldering a solid brass “horn,” tapered exponential, to the end of the barium titanate cylinder. If the large end of the horn, which is soldered to the cylinder, is 10 times the diameter of the small end, the horn acts as a transformer to increase the particle motion by a factor of 10. Hence, a 1.5‐mil motion is possible with this combination at 18 kilocycles. This structure has been made the basis of several instruments used for testing wear, for measuring magnetic flux, for testing adhesion of films, and for boring odd‐shaped holes. A feedback amplifier system with a diode limiting element is used to keep the amplitude constant.