opposed by a stepped portion s of the opposing scroll the operation of the above described compressor now will be explained with reference to fig8 a 8d as mentioned above the two spiral elements 212 and 222 are angularly and radially offset and interfit with one another fig8 a shows that the outer terminal end of each spiral element is in contact with the other spiral element i e suction just has been completed and a symmetrical pair of fluid pockets 3a and 3b just have been formed for each spiral element stepped portion s is located 1 5 u03c0 radians from the outer terminal end of the spiral element hence about three fourths of the part of the spiral element which defines the fluid pockets 3a and 3b has height h 2 and the remainder of the spiral element has height of h 1 h 2 h 3 in the stage of compression illustrated in fig8 a the end surface of transition portion t of one spiral element interfits with the end surface of the stepped portion s of the opposite scroll thus sealing off the pair of fluid pockets 3a and 3b fig8 b shows the state of the scroll members at a driveshaft crank angle which is advanced 90 u00b0 from that in fig8 a in this state contact between the transition portion t and the stepped portion s is not resolved but the line contacts between the spiral elements occur at these portions to seal off the fluid pockets fig8 c shows the configuration at a further 90 u00b0 rotation of the drive.