The Chief Justice delivered the opinion of the court.

Ueither the petition of the inhabitants of LaVilla, nor the order of the Commissioners, assert or find that the limits of the town of LaVilla “ include an undue amount of vacant or farming lands.” neither does the board find that the boundaries of LaVilla are of “ unreasonable and unnecessary extent,” unless that may be implied from the making of the order curtailing the proportions of the town.

On the contrary they find that the detached portion in*350stead of being “ unreasonably and unnecessarily ” included within the limits of an incorporated town or city, as “ vacant or farming land,” very proper territory to be included within such corporation, and forthwith proceeded to order that it be included within the limits of the adjoining city of Jacksonville.

The entire purpose of the act, so far as it relates to curtailment of boundaries, seems to be to ascertain whether “ the boundaries of such town or city are extended beyond necessary and useful limits and include an undue amount of vacant or farming land,” and then to prescribe new boundaries and thus “ limit the corporate authority,” as expressed in the words of the act.

It is a well established rule that the proceedings of all tribunals created by law, and whose powers are prescribed by law, must he shown to be within the powers expressly granted, and that acts done by them not within the prescribed limits are nugatory. It is unnecessary to cite authorities upon this familiar proposition.

The clearly expressed object of the act was that of relieving unoccupied and farming lands included within the limits of a municipal corporation from the burthens of taxation for municipal purposes, for which the owners of the lands did not enjoy adequate benefits, and the jurisdiction over which land was not necessary or useful to the corporation.

The power of the Board of County Commissioners in the premises was to inquire, inspect and thereupon determine upon their individual judgment whether these were vacant or farming lands, and if so whether the boundaries were of unnecessary or unreasonable extent.

Nothing in the record of their proceedings appears showing that these matters entered into or controlled them, or that their order was v based upon any such considerations. *351Tlieir order appears to have been au arbitrary act, made irrespective oí the clear purposes of the statute. It was a mere dismemberment of a portion of one corporation for the purpose of enlarging the boundary of another. However meritorious' the object to be attained, it was not within the contemplation of the statute.

It follows ’that the order of the County Commissioners was unauthorized and void.

It was claimed on the part of the respondent that the act in question was unconstitutional because it attempted to confer judicial power upon the Commissioners, creating a court to “ hear, try and determine” matters by the exercise of judicial functions. However unnecessary it may be to determine this point, (as the decree of the Chancellor is sustained upon the' ground already stated,) we think this position not tenable. The power of the County Commissioners as conferred by the act of 1877, Ch. 3025, was not strictly judicial within the prohibition of the Constitution.

Like the power to hear and determine applications to lay out, open and discontinue roads, locate and build bridges, and similar powers and duties, they merely exercise such judgment and discretion, adopting such measures under the law as to them may seem conducive to the public convenience and public needs. Indeed, to deny the power of the Legislature to confer such duties upon ministerial officers, in the performance of which duties they merely exercise a discreet judgment with reference to the convenience and interests of the public, would have the effect to abrogate nearly if not quite all the powers and duties usually exercised by County Commissioners in conducting the ordinary business of the county.

The decree is affirmed with costs against appellants.