Let the principal answer.
The application of this rule arises chiefly out of the relation existing between the parties in the cases of principal and agent, and master and servant. An instance whereof, is where a servant commits a trespass by command of his master ; the servant is, in such case, himself liable as directly committing the trespass, and the master asunder this rule, “Respondeat superior” So in the case of negligence, as also in all tortious acts by a servant or other agent acting under the authority, express or implied, of his principal.
The rule applies also to cases of fraud on the part of the servant acting apparently within the scope of his authority, but it does not apply to wilfully tortious acts, as acts of purposed injury not falling within the scope of such authority. Nor does it apply to acts of negligence on the part of the servant not arising immediately out of the business in which he is engaged on behalf of his master ; as where A gratuitously permitted the use of his shed to B for the purpose of the latter having a job of carpentering work done in it by his workman, and the workman whilst so employed accidentally dropped a match with which he had lighted his pipe, and thereby set fire to the shed ; it was held that B. was not responsible for such damage, though the jury found that the fire was caused by the negligent act of B.'s workman. But it seems that it would have been otherwise if the workman in the course of his employment had been guilty of any negligence at all applicable to the employment in which he was engaged.
The master is liable, even though the servant in the performance of his duty is guilty of a deviation from the strict line of it, or a failure to perform it in the most strict and convenient manner ; but, where the servant instead of doing what he is employed to do, does something not warranted by his employment, the master cannot be said to do it by his servant, and so is not responsible for the negligence of the servant in doing it. If a master, in driving his carriage, from want of skill causes injury to a passer-by, he is responsible for the injury done through that want of skill ; so, if instead of himself driving, he employs his servant to drive, the servant is but an instrument in his hands, and what the servant so does in furtherance of his master's will, is the act of the master according to the rules, “Qui facit per alimn facit per se,” and “ Respondeat superior.”
Public functionaries, as judges, magistrates, etc, are not liable for the illegal or wrongful acts of their inferior ministerial officers, provided they themselves act within the scope of their authority, but otherwise if not within the scope of such authority. Nor is any servant of the Crown liable in such case. Nor does the maxim apply to the Crown itself. A municipal corporation are, however, liable for the negligent acts of their servants ; as where, in laying down gas pipes, a piece of metal being chipped out, it struck against the plaintiff's eye, whereby he lost his sight.
The principle of the rule, however, does not apply where the party sought to be charged does not stand in the character of employer to the party by whose negligent act the injury has been occasioned ; as, if I agree with a builder to build me a house according to a certain plan, he would in such case be an independent contractor, and I should not be liable to strangers for any wrongful act done by him in the performance of his work.