On proof of certain facts principal not liable for the acts of his agents

On the trial of any person as principal for publication by his agent of words alleged to have a seditious intention as defined in section 215 such person shall be entitled to be discharged if he proves that– (a) the publication was made without his authority, consent or knowledge; (b) the publication did not arise from any want of due care or caution on his part; and (c) he did everything in his power to assist in ascertaining the identity of the person responsible for writing and publishing respectively such words.