Regarding taxing statutes, the well established rule is, 'if the person sought to be taxed comes within the letter of the law he must be taxed, however great the hardship may appear to the judicial mind to be. On the other hand, if the crown seeking to recover the tax can not bring the subject within the letter of the law, the subject is free, however apparently within the spirit of law the case might otherwise appear to be'. Such a construction is known as: