(After Stating the Pacts as Above). — This action is brought under the Employers’ Liability Law of this state (Civ. Code 1913, §§3153-3162). Appellant makes thirteen assignments of error, which raise two main questions: First. Does the work in which appellee was engaged at the time he sustained the injury bring the case within the provisions of the Employers’ Liability Law? Second. Was the injury caused by the negligence of the appellee?

Subdivision 7 of. paragraph 3156, Revised Statutes, of Arizona 1913, classifies “all work in the construction, alteration, or repair of pole lines for telegraph, telephone or other purposes” as hazardous within the meaning of the Employers’ Liability Law.

. Appellant contends that the first question should be answered in the negative, first, for the reason that the trimming of trees is not such work as comes naturally in the construction of a pole line, but is work outside of the construction of a pole line; and, second, that the evidence does not show that the accident in which the appellee was injured was due to a condition or conditions of the hazardous employment of constructing or repairing pole lines.

Appellant assigns as error the following instruction given by the court:

“And in this connection, gentlemen, I instruct you that any work which was necessary to be done for the construction of the pole line for telegraph, telephone, or other purposes, would be work done in the construction; that is, anything that was necessary in order properly to construct this line, and for that *354 purpose would Tbe considered work done in this occupation. ’ ’

We think the evidence fairly shows that the trimming of these trees was a necessary and indispensable part of the construction of the pole line. True, as urged by appellant, the employee was subject to no greater hazard than would be the employee of a farmer who was trimming trees for firewood; but this court is not concerned with the details of the work where it appears from the evidence that the specific work being done is an indispensable part of the hazardous occupation declared by statute. We think the instruction given by the court is too broad. We do not believe the jury should have been instructed that “any work which was necessary to be done for the construction of the pole line would be work done in the construction,” nor that “anything that was necessary in order properly to construct this line, and for that purpose, would be considered work done in this occupation.” The instruction is too broad, as it might include such preliminary work as a survey, or the hauling out of materials, or other preliminary work which is necessary to be done in order to construct a pole line, but yet not really work in the construction. However, in this case we consider the instruction harmless, for the reason that, the evidence being uncontradicted upon this point the court can determine as a matter of law that the labor in question was work in the construction of a pole line.

As to the contention of the appellant that the accident was not due to a condition or conditions of the hazardous employment of constructing or repairing pole lines, we think this case is distinguished from the case of Gillis v. Graeber, 26 Ariz. 34, 221 Pac. 235. In the Grillis case the employee was a bricklayer engaged in the erection of a brick flue and tunnel, which was in and about, and used in connection with, the ore *355 reduction works and smelter, and upon the grounds and property of the International Smelting Company in Gila county. The employer was not engaged in the operation of a mine or smelter. The court says that, before the employee can recover from the employer, he must have been injured while working in the employer’s occupation, as classified in paragraph 3156 of the Revised Statutes, and in the course of the opinion this language is used by way of illustration:

“If the employer’s occupation is the construction, alteration, or repair of pole lines for telegraph or telephone, and the employee was hired to assist in such work, he must show he received his injury in his employer’s hazardous occupation.”

In this instance the employer, the appellant in this case, was engaged in the construction of a pole line which was to be used as an electric transmission line. If the trimming of trees was an integral part of that construction, as it appears from the evidence that it was, then it is apparent under the decision in Gillis v. Graeber, supra, that this case is easily distinguished from the illustrations cited by counsel for the appellant, where they presuppose that this trimming of trees might have been done by an independent contractor, or the same class of work might have been done by a farmer who was trimming trees for firewood.

The statute reads:

“All work in the construction, alteration or repair of pole lines for telegraph, telephone or other purposes.”

The case of Consolidated Arizona Smelting Co. v. Egich, 22 Ariz. 543, 199 Pac. 132, holds that:

“The condition or conditions that cause the accident resulting in injury or death may be inherent in the occupation, or they may arise from the manner in which the business is carried on. The conditions of *356 the occupation in which the employee does his work involve, not only the place he works, but the tools with which he works, the one as much as the other. He cannot perform his work without tools, nor without being in the place assigned to Mm.”

In this case it is apparent that the work above ground in trimming trees is hazardous just the same as climbing poles, and, it being a part of the work of construction, it appears to us that the injury suffered in this case was due to a condition or conditions of the employment.

The second question raised by appellant must, we think, be answered in the negative. There was evidence to show that the appellee might very well have taken a rope, climbed the tree, tied the rope around the limb, returned to the ground, and have dislodged the limb from the tree by pulling on the rope without danger to himself. So it appears in this case that there was an unsafe way to do the work and another way which perhaps might have been safe. In the case of Tom Reed Gold Mines Co. v. Morrison, 26 Ariz. 281, 224 Pac. 822, this court used the following language:

“The mere fact that one selects voluntarily the more dangerous of two ways of doing a thing does not of itself as a matter of law constitute negligence. . . . Whether, therefore, the injury was due to appellee’s negligence in choosing the less safe method ... or to a condition of his employment was a matter falling peculiarly within the province of the jury to decide. ’ ’

So in the instant case the question of negligence became one of fact for the jury.

Appellant complains of the following instruction given by the trial court:

“You are instructed, gentlemen of the jury, that the plaintiff has the burden of showing that the acci *357 dent which caused his injury was not caused by his own negligence. Hence, unless you find as an affirmative fact that the accident which caused plaintiff’s injury was not caused by the sole negligence of the plaintiff, your verdict must be for the defendant.”

We cannot approve the form of this instruction, for the reason that in the last sentence two negatives are used, thus making the instruction confusing to the jury. Webster defines the word “unless” as—

“Upon any less condition than; if not; supposing that not; if it be not; were it not that.”

The last part of this instruction, translated, might therefore well read:

“Hence, if you do not find as an affirmative fact that the accident which caused plaintiff’s injury was not caused by the sole negligence of the plaintiff, your verdict must be for the defendant.”

—which would still be confusing. The instruction being not entirely clear on account of the double negative, we do not recommend it to trial courts. The one clear thing about the last sentence of the instruction is, “your verdict must be for the defendant.” Hence the error tended to favor rather than prejudice the appellant with the jury, and is therefore harmless.

Appellant makes particular complaint of this instruction on account of the use of the word “sole” before the word “negligence.” The use of the word “solely,” in an instruction somewhat similar to this, was discussed at length in the case of Young Mines Co., Ltd., v. Blackburn, 22 Ariz. 199, 196 Pac. 167. It is within the knowledge of the writer that the trial courts of this state have been frequently using the form of instruction there approved. While we believe that the word “sole” or “solely” .might well be omitted from these instructions, we do not desire to *358 change the ruling there made, and consider further discussion of the subject unnecessary.

The judgment is affirmed.

McALISTER, C. J., and ROSS, J., concur.

Note. — Judge LOCKWOOD, having tried this case in the lower court, took no part in this decision.