The defendants acted under the authority of the surveyors of highways of the city of Lowell in what they did as to certain buildings standing in the streets of that city. They have not converted them to their own use, unless they did so by taking them down and removing the materials from the streets, and they have always been ready to deliver these to the plaintiff.
It is contended that no question of the construction or repair of highways is here involved, and that only a jury can decide whether the use made by the plaintiff of the streets in moving his buildings through them was unreasonable and such as to amount to an obstruction of the ordinary course of public travel. If this were a controversy between the plaintiff and persons acting without public authority in removing these buildings as an obstruction to their own lawful use of the street, such would undoubtedly be the case; because private persons so acting take the risk of being deemed and treated as trespassers, unless they show that they are justified in what they do in the exercise of their own rights. The cases cited by the plaintiff go no further than this. Hopkins v. Crombie, 4 N. H. 520, 525. Graves v. Shattuck, 35 N. H. 257.
There may be a use of a highway, so unreasonable in its character as to amount legally to an obstruction of it, even if the public travel can still be continued over it. It is the right and duty of the surveyors to remove whatever obstructs or incumbers a highway, or hinders, incommodes or endangers those travelling thereon. Gen. Sts. c. 44, § 8. This authorizes them to remove not only a structure which permanently, but one which temporarily, obstructs the way, as it does to remove the piles of rubbish or of goods, with which it may be incumbered. Day v. Green, 4 Cush. 433, 437. Whether that which is found in the highway constitutes an obstruction is to be determined by them, and their decision is not liable to be afterwards revised by a jury. Benjamin v. Wheeler, 15 Gray, 486, 491. Heald v. Lang, 98 Mass. 581. Bay State Brick Co. v. Foster, 115 Mass. 431. If it were otherwise, although acting as public officers, they could only so act at the risk of being afterwards treated as trespassers, and the highway would necessarily in some instances continue obstructed, while the character of that which might finally be *573determined to be a nuisance was being discussed and considered by the judicial tribunals.
It is said, however, that, even if the removal of the buildings by the surveyors was authorized, they had no authority to destroy them. Without considering whether the decision of the surveyors as to the mode of removal is or is not conclusive, it is sufficient that it has been found as a fact by the jury that the taking down of the buildings was a reasonable mode of removal under the circumstances, and therefore that what they had a right to do has been properly done and with due regard to the rights of the plaintiff. Nor was it erroneous in the presiding judge to rule that, in determining whether the mode of removing the buildings adopted was reasonable, the jury were to consider that the plaintiff had no right to have them in the highway. This assumed only that the adjudication by the surveyors, that thus situated they were an obstruction to the public travel, was conclusive, and that the plaintiff could not of right demand that they should be moved entire upon his Elm Street lot or any other distance through the streets of the city.
The evidence that the motive of the surveyors, or of one of them, in making their order, was that buildings of this class should not be placed upon Elm Street, was not relevant. An act, done within the scope of a public officer’s lawful authority, does not become illegal by reason of the motive which may have influenced his mind in doing it. Benjamin v. Wheeler, ubi supra.
It is unnecessary to consider whether the mayor and aider-men could properly issue a license for the removal of buildings through the streets of the city, which would control the surveyors in the performance of the duty imposed upon them by the general law. If such license could properly have been issued, it is clear that, to be of any avail, its conditions must be complied with. The license issued required the buildings to be “ moved without delay,” and it is found by the jury that they were permitted to “ remain in the street longer than would have been necessary, if the plaintiff had exercised reasonable diligence in their removal.” It further appears that he was engaged in moving them, and proposed to move them, in a different way from that provided by the license. The license of the plaintiff *574was revoked on April 27, of which he had notice on April 28. On April 29 he was notified by the surveyors that his buildings incumbered the street and that he must remove them within thirty-six hours, and no act was done by the surveyors to interfere with his occupation of the street until May 1.
Judgments on the verdicts.