Looking, then, at the scope and purpose, the object, of s. 17 (3), one must ask whether its intention is to compel those who have the ultimate control of power cranes to do anything, or to refrain from doing anything, for the benefit of persons who will be exposed to danger by its contravention. If it had prescribed safety measures to be observed in the driving of power cranes, either specifically identifying the measures or, as in Butler (or Black) v. Fife Coal Co. Ltd. [4] requiring in general terms the observance of due care and diligence, the conclusion might not be difficult that, by making compulsory the measures so described, the statute by implication created correlative private rights to have them observed. But s. 17 (3) makes nothing compulsory save the holding by the driver of a certificate of competency. The legislature, in enacting this particular provision, has elected not to address itself to the topic of the taking of precautions in the interests of persons whom the driving of power cranes might endanger. The protection of such persons from the results of incompetency or untrustworthiness in the driving of power cranes is, clearly enough, the ultimate objective by reference to which the enactment of the provision is to be explained in terms of legislative policy. But the legislature has chosen to serve the end in view, not by requiring crane-owners to restrict the driving of cranes to competent and trustworthy persons, but by providing for a governmental check upon the competency and trustworthiness of drivers and, in order to render the check effective, making the holding of a certificate as to the result a statutory prerequisite of employment, instruction or permission to drive a power crane. The common law places upon a person who causes machinery to be used a duty to take reasonable care for the safety of persons imperilled by its use, and that duty is left by s. 17 (3) without addition or subtraction. All that is done is to provide for proof of a person's competence and trustworthiness to the satisfaction of officers of the government before the person may be allowed to drive a power crane. It is impossible to maintain as propositions of fact that until he gets his certificate he is incompetent or untrustworthy, and that the grant of the certificate makes him competent and trustworthy. In the Supreme Court the suggestion was made that the Act operates to create, upon the issue of a certificate, a statutory competency where before there was statutory incompetence; but there is nothing in the Act to support such a doctrine, and it cannot be accepted. In the final analysis the question whether s. 17 (3) creates private rights depends upon the answer to be given to the second of the questions raised by the appellant's argument, namely, the question whether there can be a causal relation between, on the one hand, the lack of a certificate on the part of a person who is allowed to drive a power crane and, on the other hand, an injury sustained through the driving of the crane by that person.