The first error, complained of is that the Commission considered an unsworn statement by a safety inspector, which was in the Commission’s files, but which was not disclosed to the plaintiffs until discovered in *411the record returned by the Commission to the circuit court. If the award cannot be sustained except by reference to this report, we think the contention of the plaintiffs is right and should prevail. The attorney general concedes that, but contends that reference to the report is not necessary to sustain the findings, and wé so hold.

The statute under which treble compensation was awarded is sec. 102.09, sub. (7), which provides:

“Compensation and death benefits, as provided in sections 102.03 to 102.34, inclusive, shall, in the following cases, be treble the amount otherwise recoverable: . . . (b) If the injured employee be a minor of permit age, or over, and at the time of the accident is employed, required, suffered or .permitted to work at prohibited employment.”

Oiling or greasing a hazardous machine while in motion is a prohibited employment. Sub. (3) (b) 10, sec. 103.05.

It is the 'contention of the plaintiffs that Blum was not employed, required, suffered, or permitted to oil or grease dangerous machinery while in motion. The claimant, with respect to the oiling, testified:

“He asked me if I could run it and I said ‘sure.’ I greased and oiled that machine every morning before -the accident that I ever ran it. I thought it was my duty if I ran the mixer to grease it. The foreman had been there when I greased it. . . . There was a knock and I didn’t know just where it was, and that morning I hadn’t had time to grease the mixer so I— there was a couple of grease cups I had forgotten and I went back there and started turning them. I was using my left hand, and a fellow is a little awkward with that hand, and I had it all greased and was pulling my hand out and a fellow dumped a concrete dumper mixer and I turned toward him and drew my hand toward me. My hand got caught in the gears and the engine choked. ... I saw that they always greased the mixer in the morning before they started. I suppose the gears themselves had been greased where this guard was over them, aS well as the grease cups on the shaft. ... I remember seeing the operator grease this particular grease cup where I got hurt *412in-the morning before the machine started, as well as the other grease cups, and then sometimes I would help' out by turning the crank, and sometimes he would turn the crank and I would work the carburetor. . . .

“I hadn’t ever seen anybody grease this mixer while it was running or any other mixer. Mr. Walters didn’t give me any instructions to grease it while it was running and he didn’t say I shouldn’t, either. I knew that the other mixer operators did the greasing in the morning before they started. I never saw any of them grease it while it was running. I knew that was the general and regular practice and that was the way to do it. That is, to grease it before starting in the morning.”

In view of the findings of fact made by the Industrial Commission, we must assume that the, employer did not instruct the claimant not to grease the machine while it was in motion. Therefore the case stands this way: A boy seventeen years old is employed to operate a concrete mixer. He has received no instructions from his employer in respect to greasing or oiling the machine. He has never seen any one attempt to grease or oil a machine while it was in motion.' While he is operating the machine, deeming it a part of his duty to oil and grease it, he becomes convinced by reason of a knock in the machine that it requires greasing, and as a part of his duty as operator attempts to grease it while in motion and is injured. Under such circumstances cán the finding of the Industrial Commission that he was employed to' grease hazardous machinery in motion be sustained?

In the solution of this question we get little if any help from adjudicated cases. No claim can be made that the act performed by the claimant was not done in the course of his employment and for the benefit of his employer. Nothing in the terms of his employment limited his work in any particular. He was simply to operate the machine. We are of the opinion that where a person is employed to operate an independent piece of machinery and his duties as such operator include oiling and greasing the machine, *413and there is no express direction or prohibition with respect to the time and manner in which such oiling and greasing is to be done, it is a natural and reasonable incident to his employment that the operator oil or grease the machine if it needs it while it is in motion. The greasing of the machine was a part of his duty as operator, and whether he did it while at rest or in motion was left to his. discretion. There is nothing in the conduct of the claimant indicating that the injury was one intentionally self-inflicted. The greasing of the machine being an incident to his employment and the time and manner of doing it being left to him, he was employed to perform the act he was engaged in at the time he sustained his injury. Therefore the finding of the Commission must be sustained without reference to the. report of the inspector.

The holding in this case is confined to the facts presented here. If the claimant had been employed definitely to do nothing but operate the machine and had been directed not to attempt to oil or grease it while it was in motion, a different question would be presented. The claimant here did just exactly what a seventeen-year-old boy would be likely to do under, all the circumstances. Because boys of that -age are apt to undertake just such things as the claimant did in this case, the legislature enacted this law prohibiting their employment in the specified occupations. The trial court said: “It is common knowledge that one who runs a machine is expected to look after such details of operation as oiling and greasing. Applicant thought it was his duty to grease the mixer if he ran it. One who places an employee in control of the operation of a machine is charged with knowledge of the fact that such employee will do. such things as are customarily done in the operation of such a machine. The proof warranted the Commission in finding that the applicant was never directed not to oil the mixer while in motionand correctly held that the finding of the Commission must be sustained.

By the Court. — Judgment affirmed.