Residual velocity field as before but only for Arm 1. Printed in red and black are respectively the prograde and retrograde rotators from the S/N ≥ 10 sample. The contours give the cloud sizes and shapes. As can be seen, most clouds enter the arm (redshifted side for Arm 1) as prograde rotators and come out as retrograde rotators. The same is seen in Arm 2 and in the lower S/N sample (see last part of Table 2) but there are too many clouds for a simple visualization.