In 1847 George Lewis Smyth wrote [in Ireland: Historical and Statistical Vol II Whittaker and Co, London 1847 Chapter 14]
Another favourite object of praise and assistance is the Dublin and Kingstown Railway. The large sums lent to this railway and to the Ulster Canal are represented in certain circles in Dublin to have been matters of personal obligation. A capitalist holding a considerable interest in both undertakings is familiarly described as always carrying a commissioner in his breeches pocket.
Who was the capitalist in question? One possibility is Peirce [or Pierce] Mahony, solicitor to both the Dublin and Kingstown Railway and the Ulster Canal Company, but perhaps “capitalist” in not quite the mot juste for him. Another is James Perry, quondam director of the railway and Managing Director of the Ulster Canal Steam Carrying Company, which was owned (from 1843) by William Dargan, the contractor who built the Dublin and Kingstown Railway.
Perry had fingers in many other pies, including the Ringsend Iron Works which, in 1842, built an iron steamer for the use of the City of Dublin Steam Packet Company on the Shannon. The steamer was named the Lady Burgoyne.
Irish waterways history 
Interesting. I didn’t know that Pierce Mahony was connected to the Ulster Canal (I was aware of his name from the D&KR). One economic success matched by an economic failure!
Mahony was another top-class fixer. The reference for his UC involvement is Dublin Evening Post 24 November 1835 (I haven’t looked for further mentions).
There is an interesting book on the Irish canals in TCD Early Books Library (Gall Z. I. 98.) it seems to set out the rules under which the canals were built.