In the case of deeds conveying property lying partly within and partly without the County, the tax shall apply only to such proportion of the consideration paid or to be paid as the value of the property within this County bears to the value of the whole property conveyed. Upon deeds of trust or mortgages conveying property lying partly within and partly without the County, the tax shall apply only to such proportion of the debt secured as the value of the property within the County bears to the value of the whole property conveyed.