The international comparison of frequency standards made with the luminous quartz resonator shows the different laboratories,-Physikalischtechnische Reichsanstalt, National Physical Laboratory, Bureau of Standards, and Electrotechnical Laboratory,-to be in agreement to one part in 105 when used to calibrate the resonator at its flexuralfundamental of about 10 kc, due allowance being madefor the temperature coefficient of the resonator in this mode, namely, about 1 part in 105 and negative. The observed agreement seems limited by the luminous glow resonator used rather than by any difference between the laboratory standards compared.AST year the writer had an opportunity of making an international comparison of frequency by means of a luminous quartz resonator. The quartz resonator (No. 108/77.9) was made by the Loewe Radio Company of Germany. The quartz bar, as illustrated in Fig. 1, is enclosed in a partially evacuated bulb, and is a bar of Curie cut (X-cut).The thickness of the quartz bar along the X axis (electrical axis) is 0.15 cm, its length along the Y axis is 8 cm, and its breadth along the Z axis (optical axis) is 0.4 cm. The bar is held in position by silk threads at a distance of 1 cm from each end and has four electrodes, the lengths of which are approximately 2.4 cm each. Terminals (1) and (4) of the resonator are connected to one of the terminals of the coupling coil provided, and terminals (2) and (3) to the other terminal of the coil. The coupling coil has an inductance of 158 mh and a resistance of 88 ohms.The frequency fb of flexural vibration of the bar in the direction of the Z axis is theoretically k2xiV Z fb = -' 4rV/3 y2 in cycles per second where k is (m+j)-r; y and z are the lengths of the bar in cm along the Y and Z axes respectively; v denotes the propagation velocity of elastic waves in quartz in cm per sec. Putting v = 5.4
