620,184. Condensers. GRIFFITHS, H. A. H. Dec. 17, 1946, No. 37190. [Class 37] A condenser having a capacity remaining constant on change in temperature is mounted within an insulating envelope 9, e.g. of leadglass and has electrodes 13, 15 disposed partly within one another so as to overlap co-axially along the axis of the electrodes, the shapes and arrangements of the electrodes being such that on temperature change variations of the dimensions of the electrodes cause no change in capacity; and the substances and dimensions of the envelope 9, the electrodes and electrode mountings are such that a variation in the lengths of the electrodes on temperature change is compensated by a variation in the length of the envelope, so that the overlap of the electrodes is held constant. Each electrode comprises two copper cylinders on an end plate 17 attached by a non-expanding nickel-steel rod 19 to a copper end cap 21 sealed to the envelope. Overlapping co-axial electrodes of square, triangular or other cross-section may be used. According to the Provisional Specification, the condenser may have a positive or negative temperature coefficient.