Section 11. That the second section of an act entitled "An Act to establish a uniform line along the river Delaware in front of the incorporated district of the Northern Liberties and Kensington, in reference to county bridges and for other purposes, enumerated in the title to the same," approved the sixteenth day of April, one thousand eight hundred and forty- eight, whereby an action for work, labor, and service done and performed, and materials found and delivered in cases where bridges have been or may be erected for a county, and deviations from or alterations in the plan contracted for have been made by the directions of the county commissioners, and the commissioners and the builder cannot agree upon the compensation, be, and the same is hereby repealed: Provided, That the repeal of this act shall operate upon contracts, express or implied, made with the commissioners of Lehigh county alone.