pro read_velocities
@common_blocks.inc
  old_var_index = var_index
  if vel.read eq 1 then return
  cons_vel = fltarr(2)
; find velocity fields         
   sds_in = var_index
  found_at = 0 
  FOR i=0,N_ELEMENTS(list_str)-1 DO BEGIN
; magnetic field or velocities?
      if (vector_field_b GT 0) then check = STRPOS(list_str(i),'Bx') else $
               check = STRPOS(list_str(i),'elocity') 
      pcheck = STRPOS(list_str(i),'articl') 
      if ((check ge 0) and (pcheck eq -1) and (found_at eq 0)) THEN found_at = i
   ENDFOR
; assume it is 3D and the following are y and z
  os = where(slice_ori lt 1.e-15)
  IF (N_ELEMENTS(os) eq 2) THEN BEGIN
     sds_num =  found_at + os(0) + 1
     var_index =  sds_num - 1
     vel_one = construct_interpolated_slice_data()
     sds_num =  found_at + os(1) + 1
     var_index =  sds_num - 1
     vel_two = construct_interpolated_slice_data()
  END         
  sds_num =  sds_in
  var_index =  sds_num - 1
  vel.read = 1
  var_index = old_var_index
  RETURN
END 
;.compile read_velocities.pro