function LOGTICK,axis,index,value
; This function will provide tick labels which are powers of 10
	exponent = alog10(value)
	if((exponent mod 1.) ne 0.) then begin
		print,!msg_prefix+'Tickmark value not an integer power of 10.'
		print,!msg_prefix+'Routine LOGTICK'
		pref = '~'
	endif else pref = ''
	return,pref+'10!U'+strtrim(fix(exponent),2)+'!N'
end