SUBROUTINE HYLSEW(IJ)
C     =====================
C
C     Initialization procedure for treating the hydrogen line opacity
C
      INCLUDE 'PARAMS.FOR'
      INCLUDE 'SYNTHP.FOR'
C
C     IHYL=-1  -  hydrogen lines are excluded a priori
C
      IHYLW(IJ)=0
      if(iath.le.0) return
      FR=FREQ(IJ)
      IF(FR.GE.3.28805E15) RETURN
      AL0=2.997925E17/FR
      AL1=AL0
      IF(grav.lt.6.) then
         IF(AL0.GT.160..AND.AL1.LT.364.6) RETURN
         IF(AL0.GT.506..AND.AL1.LT.630.) RETURN
         IF(AL0.GT.680..AND.AL1.LT.820.3) RETURN
       else
         IF(AL0.GT.540..AND.AL1.LT.600.) RETURN
         IF(AL0.GT.720..AND.AL1.LT.820.3) RETURN
      end if
C
C     otherwise, hydrogen lines are included
C
      IHYLW(IJ)=1
      M20W(IJ)=40
      IF(AL1.LT.364.6) THEN
         ILOWHW(IJ)=1
         FRION=3.28805E15
       ELSE IF(AL1.LT.820.) THEN
         ILOWHW(IJ)=2
         FRION=8.2225E14
       ELSE IF(AL1.LT.1458.) THEN
         ILOWHW(IJ)=3
         FRION=3.6544142E14
       ELSE IF(AL1.LT.2278.) THEN
         ILOWHW(IJ)=4
         FRION=2.0555837E14
       ELSE IF(AL1.LT.3281.) THEN
         ILOWHW(IJ)=5
         FRION=1.315589E14
       ELSE IF(AL1.LT.4466.) THEN
         ILOWHW(IJ)=6
         FRION=9.136394E13
       ELSE 
         ILOWHW(IJ)=7
         FRION=6.7120228E13
      END IF
      IF(FRION.GT.FR) M10W(IJ)=int(SQRT(3.289017E15/ABS(FRION-FR)))
c     WRITE(6,601) ILOWH,M20+1
c 601 FORMAT(1H0/ ' *** HYDROGEN LINES CONTRIBUTE'/
c    * '     THE NEAREST LINE ON THE SHORT-WAVELENGTH SIDE IS',
c    * I3,'  TO ',I3/)
      RETURN
      END