The arrival of Arthur McMahon at Paris is specially noted in Tone's Diary on February 1, 1798.[674] Soon after the Hamburg spy announces, with other facts, that McMahon—O'Coigly's companion—is appointed colonel and aide-de-camp to Napper Tandy.[675] A later letter of secret information, no doubt from Turner—who had been a colleague of McMahon when organising treason in Ulster—says:—
MacMahon has about 300l. sterling, property remitted him by Charles Rankin of Belfast; this he means to employ in buying a farm. Tired of politics,[676] especially those of France, he is to write to Citoyen Jean Thomas, à la Poste restante, à Hamburg, whom he looks on as a good patriot.
The 'Castlereagh Papers' give a secret account of Tandy's expedition; and how 'Joseph Orr and McMahon the clergyman, went out in a small corvette of eight guns, to reconnoitre the Irish coast and to fire signals; but the boat turned leaky, and they were obliged to put into Flushing, being chased by the English cruisers. These two refused to go any more, and went to Boulogne, where they follow privateering.'[677]
This is the last we hear of McMahon until he turns up in the letter of Berthier, the French Minister of War.
It would have been well for McMahon's friends had the quondam shepherd entered on pastoral work of another sort, assuming that he seriously entertained the idea, and that it was not mooted by him to throw Turner off the scent. Turner—at this time—had begun to be suspected, as Reinhard shows (ante, p. [53]). Certain it is, the soi-disant farmer chose dirtier work than scouring drains, or even spreading manure. But as his movements with Tandy are secretly reported to the British Government, it would seem that he had not as yet become a regular informer. Whatever proposal he made to Pitt, the bargain was apparently bungled. Unlike others, his name is not to be found in any pension list. Judging from the poverty in which Bernadotte found McMahon in 1803, his trade as a spy cannot have been very remunerative. But increased trade often brings large profits, and his opportunities for doing good work for Pitt were certainly greater after 1804.
Experience taught McMahon something. A disappointed man, willing to spy on behalf of whichever side paid best, had at least no difficulty in making a choice. How he gradually acquired facilities for plying his trade with profit now remains to be shown.
Miles Byrne—who held a command in the rebel lines at Vinegar Hill, narrowly escaped with his life, was afterwards the trusted agent of Robert Emmet in 1803, and became a colonel in the French service—supplies in his Memoirs an honoured list of 'exiled Irish whom he met in France,' including 'Arthur McMahon.' This would be about the year 1803. Matthew Dowling, Byrne's host on the occasion, had been deeply compromised in '98, and his name is often met in the autobiographies of Cloncurry, Hamilton Rowan, and Moore.
I spent [writes Byrne] one evening at his lodgings in company with Paul Murray and Arthur MacMahon, and he made us nearly forget we were far away from our home; he made us proud of being exiles in a good cause.
The statement of the historian of the Presbyterian Church that the Rev. Arthur McMahon embraced the military profession, and became distinguished as 'General Mack,' is true in every particular, except the last three words.