
    John Mansfield, Plaintiff in Error, versus Ebenezer Hawkes and Another.
    The establishing of a turnpike road over a general or common field is a dissolution of such common field.
    This was a writ of error to the Circuit Court of Common Pleas for this county, upon a judgment rendered by them in an action originally commenced before a justice of the peace for this county by the now plaintiff in error.
    The original action was trespass against the defendants, for taking and carrying away a cow of the plaintiff. The defendants justified on the ground that they were assessors of a general or common field, called Romney Marsh, in which the plaintiff was a proprietor; that they assessed a tax against the individual proprietors, in pursuance of a vote passed at a legal meeting of the proprietors; and that, for the non-payment of the portion of said tax assessed upon the plaintiff, they caused his cow to be taken and sold.
    At the trial of the action before the Common Pleas, amongst other things, the plaintiff produced and relied on * the act of the commonwealth, passed March 6, 1802, incorporating certain persons, with powers to lay out and make a turnpike road from Salem to Charles River bridge; 
       and he proved that more than ten years ago, and long before the making of the said tax, the said turnpike road, extending'over the said marsh three miles, and being eight rods in width, was made pursuant to the said act of the legislature, dividing the marsh into two nearly equal parts; which road still continues. The plaintiff contended that, by force of the said act or law, and of the making of said turnpike road in pursuance thereof, the said propriety was dissolved, and the said marsh ceased from that time to be a general and common field. But the court instructed the jury that the said act, and the locating and making of the said turnpike, did not discontinue or dissolve the said general field. And a verdict being returned for the defendants, the plaintiff tendered his bill of exceptions to the opinion of the court, as delivered to the jury, upon this and other points in the cause. As the court here gave no opinion upon the other points, it is unnecessary to state them.
    The instruction to the jury above mentioned was among the errors assigned. The defendants in error pleaded in nullo est erratum, and the cause was argued upon all the points at the last November term, by Merrill for the plaintiff in ¿error, and Saltonstall for the defendants in error; and at the last April term of the Court, holden at Ipswich in this county, the opinion of the Court was pronounced by
    
      
      
        Stat. 1801, c. 63
    
   Putnam, J.,

(after a brief history of the action.) The question, whether the act of the 6th of March, 1802, and the making of the turnpike road, were not a discontinuance and dissolution of the general and common field, became a material subject of inquiry ; for if the field had been discontinued, all the authority which the defendants claim to exercise over the plaintiff’s property was at an end.

* Such would have been the case if the proprietors had voted to dissolve or discontinue the' general field, pursuant to the statute of 1784, c. 53; <§> 8. That is only one mode by which a dissolution may take place. It is easy, however, to suppose that the same effect may be obtained by various other modes. If the proprietors should all agree, by deed, to discontinue such field, we see no objection to it. So, if they were to grant a way through their field, and should covenant that the grantees should enjoy it as a highway, without any obstruction from the proprietors, such a grant, being entirely inconsistent with an occupation by an entire enclosure, would necessarily operate as a discontinuance.

The case last supposed is not so strong as the case at bar. The public have acquired a way through the middle of this field. The act of the legislature, and the proceedings under it, are equivalent to a declaration, on the part of the legislature, that this field should no longer be fenced into one enclosure. It became necessary, or convenient, for the public to pass through it; and it would not be lawful for the proprietors to obstruct the public will. After the road was established, the proprietors could not lawfully shut or fence it up. Such an act would be an offence.

Suppose (which, however, is not decided in this case) that the plaintiff was, before the establishment of the turnpike road, liable to contribute, as a proprietor in a general field; he would be discharged afterwards, upon the settled rule that, where a party was bound to perform any act which the law afterwards prohibits, he shall be excused.

This view of the case, with which, after much consideration, we are all satisfied, renders it unnecessary to give any opinion as to the other exceptions made by the plaintiff.

The entry must be, that the judgment of the Circuit Court of Common Pleas be reversed, and a venire facias de nova awarded, returnable to the bar of this Court.  