Early 1830s: As the railway system began to assume an important position, Mr. Mackenzie at last determined to swim with the stream, even though it required a struggle to overcome his prejudice against the new order of things. As a result he became the contractor for the Passenger Tunnel from Edge Hill to the Lime Street station, of the Liverpool and Manchester Railway, under Mr. Stephenson.
Other contracts, on the Grand Junction, and the Glasgow, Paisley, and Greenock lines, under Mr. Locke, M.P., on the North Union and the Midland lines, under Mr. Vignoles, and on the Manchester and Salford Junction Canal, followed in rapid succession.
In 1840, he undertook several extensive contracts for the hydraulic works of the Shannon Navigation, under Mr. Rhodes. The large weir, &c., at Killaloe, the weir and lock at Mellick, the bridge and approaches at Banagher and at Shannon Bridge, the lock and weir at Roorky, with the dredging operations and deepening the shallows, were all works of importance, and attended with difficulties in their execution, which demanded all his skill and energy to surmount. The Shannon Commissioners voluntarily testified that he was the only contractor from whom they had parted without litigation of any kind.