Lines observed with the JCMT 15-m in comet 21P: two CH₃OH lines at 338 GHz on 31.3 October and one line at 350 905.100 MHz on 4.3 November 1998 UT (left side); H₂ CO at 351 768.639 MHz on 3.2 November and CS at 342 882.850 MHz on 1.3 November 1998 UT (right side). The vertical scale is the main beam brightness temperature and the horizontal scale is the Doppler velocity in the comet rest frame. The frequency scale for the CH₃ OH lines at 338 GHz is also provided on the upper axis.