Le CAPITAINE FLINDERS dit:
"In this spot he once dwelt, perhaps little known to the world, but happy."
(Comite des Souvenirs Historiques. 1897.)
Flinders' pen was very busy during these years. Access to his charts and papers, printed volumes and log-books (except the third log-book, containing details of the Cumberland's voyage), having been given to him, he wrote up the history of his voyages and adventures. By July, 1806, he had completed the manuscript as far as the point when he left the Garden prison. An opportunity of despatching it to the Admiralty occurred when the French privateer La Piemontaise captured the richly laden China merchantman Warren Hastings and brought her into Port Louis as a prize. Captain Larkins was released after a short detention, and offered to take a packet to the Admiralty. Finished charts were also sent; and Sir John Barrow, who wrote the powerful Quarterly Review article of 1810, wherein Flinders' cause was valiantly championed, had resort to this material. A valuable paper by Flinders, upon the use of the marine barometer for predicting changes of wind at sea, was also the fruit of his enforced leisure. It was conveyed to England, read before the Royal Society by Sir Joseph Banks, and published in the Transactions of that learned body in 1806.
The friendship of able and keen-minded men was not lacking during these years. There existed in Ile-de-France a Societe d'Emulation, formed to promote the study of literary and philosophical subjects, whose members, learning what manner of man Flinders was, addressed a memorial to the Institute of France relating what had happened to him, and eulogising his courage, his high character, his innocence, and the worth of his services. They protested that he was a man into whose heart there had never entered a single desire, a single thought, the execution of which could be harmful to any individual, of whatever class or to whatever nation he might belong. "Use then, we beg of you," they urged, "in favour of Captain Flinders the influence of the first scientific body in Europe, the National Institute, in order that the error which has led to the captivity of this learned navigator may become known; you will acquire, in rendering this noble service, a new title to the esteem and the honour of all nations, and of all friends of humanity."
The Governor-General of India, Lord Wellesley, took a keen interest in Flinders' situation, and in 1805 requested Decaen's "particular attention" to it, earnestly soliciting him to "release Captain Flinders immediately, and to allow him either to take his passage to India in the Thetis or to return to England in the first neutral ship." Rear-Admiral Sir Edward Pellew, commander-in-chief of the British naval forces in the East Indies, tried to effect an exchange by the liberation of a French officer of equal rank. But in this direction nothing was concluded.
Under these circumstances, with agreeable society, amidst sympathetic friends, in a charming situation, well and profitably employed upon his own work, Flinders spent over five years of his captivity. He never ceased to chafe under the restraint, and to move every available influence to secure his liberty, but it cannot be said that the chains were oppressively heavy. Decaen troubled him very little. Once (in May, 1806) the General's anger flamed up, in consequence of a strong letter of protest received from Governor King of New South Wales. King's affection for Flinders was like that of a father for a son, and on receipt of the news about the Cumberland his indignation poured itself out in this letter to Decaen, with which he enclosed a copy of Flinders' letter to him. It happened that, at the time of the arrival of the letter in Ile-de-France, Flinders was on a visit to Port Louis, where he had been permitted to come for a few days. The result of King's intervention was that Decaen ordered him to return to Wilhelm's Plains, and refused the application he had made to be allowed to visit two friends who were living on the north-east side of the island.
John Elder, Flinders' servant, remained with him until June, 1806. He might have left when there was a general exchange of prisoners in August, 1805, and another opportunity of quitting the island was presented in April, 1806, when the lame seaman departed on an American ship bound for Boston. But Elder was deeply attached to his master, and would have remained till the end had not his mind become somewhat unhinged by frequent disappointments and by his despair of ever securing liberation. When his companion, the lame seaman, went away, Elder developed a form of melancholy, with hallucinations, and appeared to be wasting away from loss of sleep and appetite. Permission for him to depart was therefore obtained, and from July, 1806, Flinders was the only remaining member of the Cumberland's company.
Throughout the period of detention Flinders was placed on half-pay by the Admiralty. It cannot be said that he was treated with generosity by the Government of his own country at any time. He was not a prisoner of war in the strict sense, and the rigid application of the ordinary regulations of service in his peculiar case seems to have been a rather stiff measure. Besides, the Admiralty had evidence from time to time, in the receipt of new charts and manuscripts, that Flinders was industriously applying himself to the duties of the service on which he had been despatched. But there was the regulation, and someone in authority ruled that it had to apply in this most unusual instance. There is some pathos in a letter written by Mrs. Flinders to a friend in England (August, 1806) "The Navy Board have thought proper to curtail my husband's pay, so it behoves me to be as careful as I can; and I mean to be very economical, being determined to do with as little as possible, that he may not deem me an extravagant wife."