Opinion by

This case was tried with care by the learned judge who presided at the trial. The charge was thoroughly impartial, and presented the questions that were submitted to the jury very clearly; but we are of opinion that the criticism made upon it by the eighth assignment of error is well founded. It held the county commissioners to a measure of accountability so strict as practically to make the county an insurer against accident happening to persons using the county bridges. The injury sued for was sustained by the falling of the roadway of the bridge into the stream while the plaintiff was crossing the bridge with his team and a load of hemlock bark. The evidence shows that the bridge was built upon a plan in common use at the time *148of its construction, and still in use throughout the state. It was built in 1877 and was in - constant use until 1888, when it was rebuilt upon the same plan. The accident occurred in 1894. But a few weeks before it happened, the county commissioners had caused the bridge to be examined, and had been present participating personally in the examination. The result of the examination was that the planks were.foundtobe decaying to such an extent as to make the roadway insecure, and they were taken up and new ones pnt in their places; but the timbers were found to be sound and the ironwork strong and safe. The roadway was supported between the abutments by means of heavy overhead truss timbers, from which seven iron rods an inch and a half in diameter descended on each side, and were secured to the needle beams on which the stringers supporting the planks were laid. The truss timbers, the needle beams, the iron rods that connected them, the stringers and the plank, were believed as the result of this examination and repair to be in good order and to make a secure structure for use by the traveling public. After the accident, an examination disclosed the fact that one of the iron rods was broken, and that part of the way across the rod the iron was discolored, indicating that so far at least the break was an old one and may have existed for a considerable length of time. The theory that prevailed at the trial and seemed best to comport with the known facts, was that this rod weakened by the concealed break had given way, and the roadway settling at that point had thrown an increased weight and strain on the other rods so that they had also given way and let the roadway fall to the stream. The question on which the liability of the county depended was whether the defect in the rod that gave way was known or ought to have been known to the commissioners.

The fact that it was not known is practically conceded. What is there in the evidence to show that it should have been known? We find nothing except the mere fact that the subsequent examination made it apparent that it had existed for some time. But this is not enough. To sustain this action, it must appear that the commissioners were guilty of negligence in the discharge of their official duties to the public. They had just made a careful examination and repair of the bridge, but neither they nor their employees discerned the defect in this rod. *149Those living near the bridge and using it most frequently had not discovered it. Its existence was not known or conjectured till the bridge fell. No method of examining and testing a structure like this has been suggested that would have disclosed the defect short of an actual taking down of the needle beams and the timbers on which the roadway rests, and the removal of the rods from their places, and their examination separately; and it is not certain that even this would have discovered the latent or concealed defect. What is it then about which the commissioners have failed to exercise the measure of care which the law imposed on them ? What have they left undone that it was their duty to do ? The measure of care and prudence required of them is the care and prudence exercised by ordinarily prudent men in their own affairs, and where the defect in a lawful structure is latent, the officers must have actual notice, to make repair a duty: Rapho et al. v. Moore, 68 Pa. 404.

The necessity for a county bridge and the precise point at which it shall be located are determined under the supervision of the court. Whether erected by the commissioners or under contract, it must be viewed and inspected by six viewers appointed by the court whose duty it is to see if the bridge has been built in accordance with the contract, or the plans, and should be paid for by the county. They report to the court of quarter sessions and their report when approved is the authority for making payment to the contractor or builder. The whole proceeding is for the benefit of the public, is conducted in the court of quarter sessions, and the important function performed by the county is to pay the cost of construction under the report of the viewers when approved by the court, and thereafter to make the needed repairs.

There was no proof in this case that justified the submission to the jury of the question whether the plan on which the bridge was built was so defective as to make its adoption an act of negligence. The learned judge did however as we understand him leave this question to the jury. He said, “ Did the bridge fall by reason of a defect in the original construction ? In other words, was it because the plan was wrong? ” The county was not bound to adopt the best known plan for bridge building. It was bound to adopt a plan approved by competent mechanics *150as suitable for the place at which the bridge was to be built, and to see that its construction was conducted by reasonably competent builders. When it was completed, it was the duty of the county to see that it was duly examined by viewers appointed by the court for that purpose, and on the confirmation or approval of their report, to pay over to the contractor or builder the price of the work and materials furnished. As this was a county bridge, we assume that it was built, inspected, approved and paid for as the law requires. No question about whether the plan was wrong seems to have been raised at any stage of the proceedings and we do not think it can be raised now. There is but one question in this case as it is presented on this record, and that is whether the commissioners ought to have known of the defect in the rod which gave way. What test should have been employed that they did not employ to determine the security of the bridge ? In what respect were they negligent ? If they examined this bridge with ordinary care and made all the repairs that on such examination were thought by themselves and their mechanics acting in good faith to be needed, they cannot be charged with negligence, and the county is not liable in this action.

The judgment is reversed and a venire de novo awarded.